Covenants 01: What Makes A Promise Unbreakable?

What separates a covenant from a contract? A look at the ancient ritual of “cutting” a promise — and why God alone walked through the blood.

When the sun had set and darkness had fallen, a smoking firepot with a blazing torch appeared and passed between the pieces. On that day the Lord made a covenant with Abram. — Genesis 15:17–18

I want to begin not with a definition but with a scene, because the Bible itself begins this whole subject with a scene — and it is one of the strangest in all of Scripture.

It is night in the land of Canaan. An old man named Abram has been promised more descendants than there are stars, though he has no children and his own body is as good as dead. And Abram does a very human thing. He asks for proof. “How can I know?” he says. And God answers him — not with an argument, not with a soothing word, but with a ritual that to our eyes looks like something out of a nightmare.

God tells Abram to bring animals — a heifer, a goat, a ram, a dove, a pigeon — and to cut the larger ones in two, laying each half opposite the other, so that an aisle of blood and flesh runs down the middle of the ground. Abram does it. All day he stands guard, driving off the birds of prey that come down to the carcasses. And then, as the sun goes down, a deep sleep falls on him, and with it a thick and dreadful darkness. And there in the darkness Abram sees something move. A smoking firepot and a blazing torch — God himself, veiled in fire — passes slowly, and alone, down the aisle of blood between the pieces.

If you stumbled onto that scene knowing nothing, you would think you had wandered into something halfway between a sacrifice and a horror. But every person in the ancient world would have understood it at a single glance, because this is how the most binding agreements on earth were sealed. They called it “cutting a covenant.” And the meaning of walking that bloody path between the divided animals was unmistakable. It was an oath sworn not in words but in flesh: may I become like these animals — may I be torn apart, may what happened to them happen to me — if ever I fail to keep my word (see Genesis 15:9-21).

That is where the storyline of the whole Bible begins to take its shape. Not with good advice. Not with a list of rules. With a God who steps down into the dark, walks between the pieces, and stakes his own life on the keeping of a promise.

In the chapters that follow we are going to walk the spine of the entire Bible — six great covenants, from a garden to an upper room. But before we touch a single one of them, we have to answer the question everything else will hang upon: what is a covenant — and what makes a promise unbreakable? And we will answer it the way we will answer every text in this book, in three movements. Promise. Person. Prayer. What God swore. How Christ keeps it. And how we stand on it to pray.

The Promise

Start with the word itself. The Hebrew is berith, and it appears in the Old Testament almost three hundred times. But notice how the Bible most often speaks of making one. It does not say “make a covenant.” It says “cut a covenant” — karath berith. You cut it, the way Abram cut those animals, because at the very heart of a covenant there is always a death, and always blood.

Now I want to free this word from something, because we have used it so casually that we have nearly drained it dry. We speak of a marriage covenant, a covenant community, the covenants buried in a mortgage. We tend to hear “covenant” as a slightly more solemn, churchier word for contract. But it is not. It belongs to a different category altogether.

A contract is an exchange between two parties, each one guarding his own interest. I will do my part if you do yours. It is built on suspicion every bit as much as on trust — which is exactly why it comes with clauses and penalties and a way out. And the moment one side fails to perform, the contract is void, and both walk away. A contract is a leash you can let go of.

A covenant is not a leash. It is a bond. It is a sworn relationship, sealed in blood, in which a person stakes his very life on the keeping of his word. You cannot break it and stroll away unharmed; you can only break it and be broken by it. A contract says, here is what I will do. A covenant says, here is who I now am to you — and may I die if I prove false.

So what is a covenant made of? When you read the covenant stories strung out across the Bible, the same four pieces keep surfacing, and it is worth naming them now, because you are going to watch every one of them reappear, chapter after chapter, all the way to the end. Not every covenant will show you all four with the same weight — one chapter will lean hard on the blood, another will have almost none; one will hang its whole meaning on a visible sign, another will have no sign at all. That unevenness is not a flaw in the pattern. It is part of what makes each covenant worth its own chapter, rather than a single lesson repeated six times.

There is, first, the oath — the word God binds himself to. And here Scripture says something that ought to stop us cold. When God made his promise to Abraham, “since there was no one greater for him to swear by, he swore by himself” (Hebrews 6:13). We swear by something greater than ourselves. But God has nothing greater. So he puts his own name, his own being, his own existence on the line. The guarantee behind the promise is God himself.

There is, second, the blood — the cutting, the death that seals the thing. The writer of Hebrews states the principle without flinching: “the law requires that nearly everything be cleansed with blood, and without the shedding of blood there is no forgiveness” (Hebrews 9:22).

There is, third, the sign — the visible seal God hangs over the covenant so that it can be seen and remembered. A bow in the clouds for Noah. Circumcision for Abraham. The Sabbath for Israel. And, at the last, a cup and a loaf of broken bread for us. Keep your eye on those signs as we go; they are a single thread the whole book is quietly weaving, and they all run toward one table.

And there is, fourth, the mediator — the one who stands in the middle, between God and the people, holding the covenant together with his own body. Noah. Abraham. Moses. David. A whole line of men standing in the gap — and every one of them pointing down the years toward the one Mediator they could never quite manage to be.

So let me set four texts in front of you, because together they show you the anatomy of a covenant better than any definition could. Watch for the oath, the blood, the sign, and the mediator.

Hear the first. It is the very scene we began with, now given its plainest words:

When the sun had set and darkness had fallen, a smoking firepot with a blazing torch appeared and passed between the pieces. On that day the Lord made a covenant with Abram and said, “To your descendants I give this land.” — Genesis 15:17–18

Watch closely who walks that aisle. By every rule of the ritual, both parties should pass between the pieces; both should swear the self-cursing oath; both should say, may I be torn like these if I break faith. But God does not let Abram walk. He puts him to sleep. And God alone, veiled in fire, passes through the blood. He takes the entire oath onto himself. He says, in effect, the curse for breaking this covenant falls on me — and on me alone. Hold that picture. Everything in this book finally comes back to it.

The second shows you the blood:

Moses then took the blood, sprinkled it on the people and said, “This is the blood of the covenant that the Lord has made with you in accordance with all these words.” — Exodus 24:8

At the foot of Sinai, young men from among the people had offered bulls as sacrifices — burnt offerings and fellowship offerings — and Moses caught half their blood in bowls and threw it against the altar. Then he read the Book of the Covenant aloud, and the people answered, "We will do everything the Lord has said; we will obey." Then he takes the second half of that same blood and sprinkles it, not on stone, but on the people themselves.

But why blood? Why should a solemn agreement be sealed in something so visceral, so unsettling to our modern sensibilities? The Bible gives us its answer plainly, in a single line: "the life of a creature is in the blood... it is the blood that makes atonement for one's life" (Leviticus 17:11). There it is. In the Bible's way of seeing, blood is not mainly about death — it is about life. The blood is the life, carried in visible form. So to seal a covenant in blood is to seal it with life itself; it is to say that this bond is not a matter of convenience or paperwork but of life and death, and that the one who breaks it forfeits the very thing the blood represents. That is why the covenant is not signed in ink. It is dashed in blood — because a covenant is a matter of life and death, and the blood says so out loud.

And notice something else hiding in the Bible's own language for this word. The Hebrew is berith, as we said; but when the New Testament writers reach for a Greek word to carry it, they choose diatheke — which is also the ordinary Greek word for a will, a last will and testament. And a will, the writer of Hebrews points out, is worthless paper until somebody dies; it never takes effect while the one who made it is living (Hebrews 9:16–17). The inheritance stays locked up until there is a death to release it. File that away. In a few pages it is going to break your heart and mend it in the same moment.

The third shows you the sign:

This is the sign of the covenant I am making between me and you and every living creature with you, a covenant for all generations to come: I have set my rainbow in the clouds, and it will be the sign of the covenant between me and the earth. — Genesis 9:12–13

A sign is a covenant made visible — something hung in the sky, or cut into the flesh, or set apart on a calendar, so that the promise can be seen long after the words that made it have faded from memory. Every covenant that follows will hand you a new sign, and I want you watching for each one, because they are a single thread the whole book is quietly weaving, and they all run toward one table.

And the fourth shows you the mediator:

At that time I stood between the Lord and you to declare to you the word of the Lord, because you were afraid of the fire and did not go up the mountain. — Deuteronomy 5:5

There stands Moses, describing his own office in so many plain words: I stood between. That is what a mediator does — he takes his place in the gap between a holy God and a frightened people, and he holds the covenant together there, often at great cost to himself. Noah, Abraham, Moses, David — a whole line of men standing in that same gap, and every one of them, sooner or later, proving too small for it, and pointing down the years toward the one Mediator who never would.

Now one more distinction before we move on, and it matters more than it looks. Not all the covenants in the Bible are the same kind. There is exactly one that is conditional — Sinai, the covenant of the Law, the one that says, “Now if you obey me fully and keep my covenant, then out of all nations you will be my treasured possession” (Exodus 19:5). If… then. That one hangs on the people’s performance, and you can already feel the tragedy folded up inside it. But the others — Noah, Abraham, David, and the new covenant that crowns them all — are unconditional grants. God binds himself, and the whole weight of the promise rests not on our faithfulness but on his.

And that is the entire meaning of that terrible night in Genesis 15. It was supposed to be both parties in the aisle of blood. But God put Abram to sleep and walked it alone. Which means your security in the promises of God does not finally rest on the steadiness of your grip on him. It rests on the oath he swore by himself, in the dark, in blood, while you were fast asleep and could add nothing to it. That is the Promise. That is what a covenant is.

The Person

Here is the second thing you must see, and if you see it, this book will never again feel like a guided tour through six unrelated agreements. It will feel like one story, told in a single breath.

These covenants are not six. They are one rope made of six strands, and every strand is knotted off at the same place — a hill outside Jerusalem, and a cross. The whole arc bends toward a single Person. That is why the second movement of every chapter will be the Person: how this particular covenant is kept, carried, and finally fulfilled in Jesus Christ.

Come back once more to that aisle of blood in Genesis 15. God walked it alone and swore the self-cursing oath: may I be torn like these animals if this promise ever fails. Remember, too, what kind of covenant this was — the one-sided, unconditional kind, resting on God's faithfulness rather than Abram's. Abram had nothing to keep.

But the family born from that promise did not stay outside every obligation forever. Centuries later, at the very mountain where we just watched Moses throw the blood of the covenant over the people, that family bound themselves to God by the other kind of covenant — the conditional one, the Law, hedged with an "if you obey… then you will be." And it was this covenant, the one with strings attached, that Israel broke — not once, but again and again, for centuries, chasing other gods and ignoring the poor and the vulnerable, until the prophets ran out of ways to warn them, and the nation was finally carried off into exile, the promised land left empty.

So ask the question the rest of the Bible exists to answer: if the very family through whom God's unconditional promise was meant to reach the world kept shattering the covenant meant to shape them into that people — what became of the oath? What happened to the curse God had called down on himself, alone, in the dark, that first night, long before any of it went wrong?

It fell. Centuries after that night, on a green hill outside the city, the God who had passed between the pieces was himself torn in two. And watch what Mark notices at the very moment he dies: “The curtain of the temple was torn in two from top to bottom” (Mark 15:38). Torn — the same violence done to those covenant animals, now done to the veil, from top to bottom, by a hand reaching down out of heaven. God bore in his own body the curse he had sworn with his own mouth, so that the promise could not break. And now you see why the writer of Hebrews made such a point of the will that takes effect only when someone has died. The inheritance God promised could be released to us in just one way: across the dead body of the Mediator.

So look at him now through every part of the covenant we have just named.

Hear the first. He is the content of every promise ever sworn — the offspring of the woman who crushes the serpent, the seed of Abraham through whom the nations are blessed, the son of David on a throne that will not end. And Paul lays his finger on the hidden grammar of it all:

The promises were spoken to Abraham and to his seed. Scripture does not say “and to seeds,” meaning many people, but “and to your seed,” meaning one person, who is Christ. — Galatians 3:16

Not “seeds,” Paul says, as though the promise meant a crowd. One seed. One Person. The whole sworn oath of God was always being carried toward a single set of hands.

The second shows you the blood — no longer the blood of a heifer or a goat, but his own:

In the same way, after the supper he took the cup, saying, “This cup is the new covenant in my blood, which is poured out for you.” — Luke 22:20

On the night before he was cut, he lifted a cup and named it. This is the new covenant — and it is in my blood. Every covenant before this one had been sealed in the blood of animals. This one would be sealed in the blood of God.

The third shows you the sign — and this time it is not hung in the sky or cut into the flesh, but placed in human hands:

And he took bread, gave thanks and broke it, and gave it to them, saying, “This is my body given for you; do this in remembrance of me.” — Luke 22:19

He took it into his own hands. On the night he was betrayed he handed his friends not a rainbow and not a knife, but bread and a cup — the last and truest of all the covenant signs, the one every earlier sign had been quietly pointing toward.

And the fourth names him for exactly what he is — the Mediator the whole long line of them had been reaching toward:

For this reason Christ is the mediator of a new covenant, that those who are called may receive the promised eternal inheritance—now that he has died as a ransom to set them free from the sins committed under the first covenant. — Hebrews 9:15

There it is, all in one verse: mediator, new covenant, promised inheritance, and a death that sets us free. Paul says it even more simply elsewhere — “there is one mediator between God and mankind, the man Christ Jesus” (1 Timothy 2:5). Moses stood between the Lord and the people at the foot of the mountain, for a moment, and then he died, and the gap opened again. Noah, Abraham, David — the same. Every mediator before him proved too small for the office. He stands in it forever.

Six covenants. One Person. In every chapter we will take that covenant and pull its thread, and follow it, and watch it disappear into his hands.

The Prayer

And now the surprise — the reason this book exists, and the thing that lifts it above a survey of Bible history. Because covenant is not only the backbone of Scripture. It is the secret engine of prayer.

Let me show you something that has been hiding in plain sight on pages you have read all your life. Go to the great intercessors of the Bible — the men and women who stood in the gap and prayed when everything was on the line — and watch how they pray. Notice what they almost never do. They almost never appeal to the worthiness of the people they are praying for. They have nothing to appeal to there, and they know it. Instead, every last one of them reaches for the very same lever. They appeal to a covenant God swore.

Hear the first, and feel the nerve of it. Moses is on the mountain. Below him the nation is dancing around a golden calf, and God has just said he will destroy them and start over. And Moses — Moses does not say, Lord, they are not as bad as they look. He says:

Remember your servants Abraham, Isaac and Israel, to whom you swore by your own self: “I will make your descendants as numerous as the stars in the sky and I will give your descendants all this land I promised them, and it will be their inheritance forever.” — Exodus 32:13

Do you see what he has done? He has reached all the way back to that night between the pieces, taken hold of the oath God swore by his own self, and held it up in front of God’s face. You bound yourself, he says. I am holding you to your own word. And God relents. The prayer that turns back the wrath of heaven is a prayer that brings God his own covenant.

The second is an old man praying in exile, with his nation in ruins and seventy years of judgment nearly spent. And listen to how Daniel opens his greatest prayer — not with his need, but with God’s character:

Lord, the great and awesome God, who keeps his covenant of love with those who love him and keep his commandments. — Daniel 9:4

The God who keeps his covenant of love. That is the ground Daniel chooses to stand on. Nehemiah, hundreds of miles from a city lying in rubble, opens his own prayer in almost exactly the same words (Nehemiah 1:5). Across centuries and circumstances the logic never once changes: God, you have bound yourself by promise — and I am bringing your own word back to you.

That is not presumption. It is the highest form of faith there is — to take God so seriously at his oath that you dare to plead it back to him. And it turns on a single, tender word that runs like a bright thread through the whole Bible: remember. God “remembers” his covenant with Noah when he sees the bow in the clouds (Genesis 9:15). He “remembers” his covenant with Abraham when he hears the groaning of slaves in Egypt (Exodus 2:24). He "remembers" his holy covenant when the priest Zechariah — struck silent months earlier for doubting God's promise of a son — finds his voice again at the birth of that son, John the Baptist, and sings out in praise (Luke 1:72). And the intercessor’s prayer, again and again, is simply to say it back to him: remember. Which means — and do not miss this, because it changes everything about how you will pray — intercession is not informing a forgetful God of something he might overlook. It is faith reminding itself of what God cannot possibly forget, and then planting its feet on it and refusing to move.

So here is the grammar of prayer this whole book is going to teach you, covenant by covenant: intercession is not about finding the right words, or working up enough feeling, or manufacturing enough faith. It is about knowing what God has sworn, and bringing it back to him. And every covenant ahead will press a different key into your hand. Eden will teach you to enforce a victory already won. Noah, to plead for the nations, for a whole world that deserves wrath. Abraham, to pray out of covenant friendship. Moses, to stand in the gap as a mediator who offers himself. David, to pray the promise back in lament, when the throne looks shattered and the facts seem to mock the word. And the new covenant, to do the most astonishing thing of all — to join a prayer already in progress.

And the third verse is the one this whole book has been walking toward. Because there is one last intercessor, and he is not in the past tense. Hebrews says of Jesus:

Therefore he is able to save completely those who come to God through him, because he always lives to intercede for them. — Hebrews 7:25

He always lives to intercede for them. Right now, as you hold this book, the Son is praying. Every intercessor we will meet — Abraham at Sodom, Moses on the mountain, Daniel in exile, the psalmist in the wreckage — was a shadow cast backward by him. And here is the gift waiting at the end of all of it: we do not pray toward a reluctant God, working up the courage to interrupt him. We pray with the Son who is already at it. We slip our small, stammering prayers into the great unbroken prayer he is praying for us at this very moment, and “since we have confidence to enter the Most Holy Place by the blood of Jesus” (Hebrews 10:19), we walk in without flinching. That is the Prayer.

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So gather it all up, and carry it home — and let me bring it home to where some of you actually live.

Some of you are carrying a promise that the facts seem to mock. You believed God for something, and the circumstances have done nothing but darken since. You feel a little like the poet of Psalm 89, who takes the very covenant God swore to David — a throne forever, a kingdom without end — and holds it up against the rubble of a fallen kingdom, and cries, “Lord, where is your former great love, which in your faithfulness you swore to David?” (Psalm 89:49). Hear me carefully: that is not a failure of faith. That is covenant faith in its hardest and bravest form — refusing to let go of God’s sworn word even when everything you can see contradicts it. We will spend a whole chapter there, with David, learning to pray like that. For now it is enough to know that the prayer is allowed, and that it is holy.

And here is the one thing I am asking you to lay down as we begin. Lay down the exhausting lie that the power of your prayers depends on you — on the polish of your phrasing, on the temperature of your feelings, on whether you can whip up enough faith to make God move. That was never the engine. It never could be; you are far too small and far too changeable to hold a promise up. The engine is the oath of God — sworn by himself, sealed in the blood of his own Son, made over to you in a will that took his death to open. That promise cannot break, because the only one who could ever break it has already borne its curse.

So over the chapters ahead we are going to learn to do what Moses did, and Daniel did, and what the Lord Jesus is doing still: to find what God has sworn, and bring it back to him. To pray not, God, look how worthy we are — we have nothing to offer there — but, God, look at your own word. Remember your covenant. You walked between the pieces. You bore the curse. You cannot deny yourself.

Let me model it, and let me pray us in to everything that follows.

Father, we come not on the ground of our worthiness — we have none to bring — but on the ground of your sworn word. You stepped down into the dark between the pieces. You took the whole oath onto yourself. And when we broke faith, you bore in your own Son the very curse you had sworn, so that the promise could not fail. So we hold your covenant up before you now. Remember your word over the ones who read this, over the situations that look like a shattered throne, over the names we carry that no one else knows. We do not pray toward a reluctant God; we pray with the Son who ever lives to intercede. Teach us, in the pages ahead, the grammar of that prayer. In the name of the One who is its answer, Amen.

And now we go back to the very beginning — to a garden, a fall, and the first promise God ever made: a single sentence of judgment spoken over a serpent, which turns out, when you lean in close, to be the first whisper of the gospel. Grace that moves first, before we have even finished hiding. 

We will meet you in Eden.