The Birth of Isaac – Gen 21

The Birth of Isaac – Gen 21

This is the story of the birth of Isaac, Abraham and Sarah’s son. Genesis records Isaac’s birth in Genesis 21, but the story starts in Genesis 11. I suppose all the way through, one question is: “can God actually keep his promises? Will he? Can he?”

Another question would be, “If God wants to build a nation, and with that nation bless every nation, why would he start with an old couple that can’t have children? Why not start with a young couple ready to have many children? Would that not be a better way to build a nation?”

Genesis 11

Before God even called Abraham in Genesis 12, we read that Sarah was childless. To make it clear, we read it another way: she was not able to conceive.

Genesis 12

Once that’s clear, God said, “Abraham, leave your father’s household, and go to a place I will show you. And here’s my promise to you: I will make you into a great nation.” At this time, Abraham was 75 years old, and Sarah was 65. They lasted a long time in those days, but still, they are not young. “I will make you into a great nation.”

Abraham and Sarah look at each other. They are along in years, no children, can’t have children, and God says, “I will make you into a great nation.” They shrug their shoulders, not sure about this, and then they start packing to move.

When they get to Canaan, this is Gen 12:7, God appears to Abraham, and says, “Look around, Abraham. I will give this land to your offspring.” Abraham thinks to himself, “It’s a very nice land, God, but the offspring part is a problem, is it not? We have no children, and it doesn’t look good.” I am guessing here about what Abraham thought. He must have thought something like that, but he kept that to himself.

Genesis 13

In the next chapter, Gen 13, God did this again to Abraham. Abraham had just let his nephew Lot pick the best of the land. Lot saw a wide plain that was well watered, it was like the garden of the Lord, it says. Lot said to Abraham, “I’ll take that.” Abraham kindly let him, and took the left overs. After Lot parted from Abraham, God spoke again to Abraham:

“Abraham, look around you. Look north and south, and east and west. All the land you can see, I will give you and your offspring forever. I will make your offspring like the dust of the earth, so that if anyone could count the dust, then they could count your offspring. Go ahead, walk around, walk all through everything you see, for I am giving it to you.”

And Abraham again thinks to himself, “it is a very nice land, God, but I don’t see how the offspring part will work. Like the dust of the earth!” For Abraham, sometimes faith was just keeping his mouth shut.

Genesis 15

Now to Genesis 15, a similar story, except this time Abraham told God what he thought. God told Abraham, “Don’t be afraid, Abraham. I am your shield, your reward will be very great.”

So Abraham explained the problem to God. “O Lord God,” he began. He was going to object to something, but he was careful to speak respectfully to God. “O Lord God, what’s the point giving me anything, since I am childless? Eliezer my servant will inherit everything I have.”  

And then Abraham said it again: “You have given me no children. A servant in my household will be my heir. O Lord God, why do you keep talking about my offspring?” Then God responded. “Abraham, that man will not be your heir. A son who is from your own body will be your heir.” Then God said to Abraham, “Let’s go outside. Come outside with me.”

So Abraham walked outside. God said, “Look up at the sky and count the stars – if you think you can.” Then God said, “That’s your offspring, Abraham. You will have that many descendants.”

And then, we read that Abraham believed God! He believed him. Abraham didn’t know how this will happen, but he was persuaded. And God said to himself, “He believed me! That is a righteous man, for sure; Abraham is a righteous man.”

Genesis 16

In Gen 16, we read about Hagar and Ishmael. This story happens when Abraham and Sarah had been in Canaan for ten years. Sarah had not had any children, but she had an Egyptian slave named Hagar.

Sarah said to Abraham: “The Lord has kept me from having children.” That’s a line, isn’t it? “The Lord has kept me from having children.” I don’t know if that’s how God saw it, but it was not far off. “So, Abraham,” said Sarah, “I will take matters into my own hands, since God is not helping. Go sleep with my slave, perhaps I can build a family through her.”

Since Hagar was Sarah’s slave, Sarah would have the right to adopt Hagar’s child as her own. That seems to be the understanding. “Perhaps I can build a family through her.” Abraham agreed, so Sarah took her slave Hagar, and Sarah gave Hagar to her own husband to be his wife.

Abraham slept with her, and Hagar became pregnant. Once Hagar knew she was pregnant, she began to despise her mistress. Hagar did not feel like a slave any more. She felt like she was the one in charge, Sarah was just trash.

Sarah did not like this. Sarah said to Abraham: “You, Abraham, are responsible for the wrong I am suffering. You have done this to me. I put my slave in your arms, and now that she knows she is pregnant, she despises me.” Sarah was so sure that she was innocent and Abraham was guilty here, that she ended with, “May God judge between you and me.”

God kept his thoughts to himself, decided just to watch this one. Sometimes Abraham did not treat Sarah very well, and other times, Sarah did not treat Abraham very well. Sounds like every long marriage. On the whole they it was a good marriage.

Abraham submitted to Sarah on this one. Sarah was not in a mood to be challenged. “Your slave is in your hands,” he said, “do whatever you think is best.” Sarah treated Hagar roughly, badly enough that Hagar fled out into the desert.

God met Hagar out there, and told her, “You go back and submit to Sarah. I will take care of you, and I will increase your descendants until they are too numerous to count.”

And Hagar in amazement said, “You are the God who sees me.” And she gave a name to God: “The One who sees me.” She thought God took care of Sarah and Abraham, but not her. But to her great delight, she found out: God is the One who sees me. That’s a keeper, isn’t it.

Harar was a nobody, an Egyptian slave. And, she had more or less brought her troubles on herself. She should not have gotten so sassy with Sarah once she was pregnant, but she did. But, God was still watching over her. “Hagar, go submit to Sarah. I’ll take care of you.” Hagar was so glad to find out that God was watching her.

She had a son, Ishmael, and the four of them lived together, Abraham and Sarah and Hagar and young Ishmael, who Abraham and Hagar’s son.

Genesis 17

Now let’s go to Gen 17. Abraham is now 99 years old. It’s been 24 years since he left his father’s household in Gen 12. We’ll pick up the story in 17:15.

God said, “Abraham, I want to talk to you about Sarah. Don’t call her Sarai any more, call her Sarah. I will bless her, and give you a son by her. She will be the mother of nations! Kings of different peoples will come from Sarah.”

Abraham fell face down on the ground, and laughed. He said to himself: “I’m a hundred, and Sarah’s ninety. It is not going to happen.” And Abraham said to God, “God, to make this so hard for yourself, just bless Ishmael.” 

God said, “Yes, I will bless Ishmael, but your wife Sarah will bear a son, and you call him Isaac. (Isaac means “he laughs.”) Sarah will have given birth to Isaac by this time next year.” For 24 years God has been saying to Abraham, “you will have offspring.” But now God gets specific. “Sarah will be the mother of this child, and within one year he will be born.” That’s Gen 17.

Genesis 18

In Genesis 18 we read that Abraham had three visitors. It is kind of hard to figure out who they are. Abraham treats them well, is a good host, makes a nice meal for them. They seem to be angels, or perhaps two angels and one of them is actually God. Not clear.

While they were eating the meal, they asked Abraham, “where is your wife Sarah?” Abraham said, “There, in the tent.” One of them said, “I will surely come and see you again, a year from now, and by then your wife Sarah will have a son.”

Sarah was in the tent behind them, listening. She heard this, and she laughed to herself, and said, “After I am old and worn out, and my lord is old and worn out, will I now have this pleasure? Will I now have this pleasure?”

The Lord God said to Abraham, “Why did Sarah laugh and say, ‘will I really have a child, now that I am old?’ Is anything too hard for the Lord? Like I said, Abraham, I will come and see you again, a year from now, and by then your wife Sarah will have a son.”

Sarah was afraid, so she lied and said, “I did not laugh.” But he said, “yes, you did laugh.” And I think he was smiling when he said that.

That’s the middle of Genesis 18. But there’s a lot of stuff in the next year, and the year is not up until Genesis 21. Genesis keeps us hanging. But eventually the year is up.

Genesis 21

Gen 21 begins, “The Lord was gracious to Sarah, as he had said, and the Lord did for Sarah what he had promised. Sarah became pregnant, and bore a son in her old age, at the very time God had said. Abraham gave him the name Isaac, he laughs.”

And Sarah said, “God has brought me laughter, and everyone who hears about this will laugh with me.” And she added, “Who would have said to Abraham that Sarah will nurse children? Yet I have borne him a son in his old age.”

In the long build up to the birth, Isaac is part of God’s promise to Abraham. But when Isaac is actually born, in the beginning of Gen 21, it is for Sarah not for Abraham. God was good to her, kept his promise to her. And that’s how she took it. “God has brought me laughter.”

Sarah was so glad that God had done this for her, and she was pleased that she could do this for Abraham, give him a son in his old age. And that, people, is the story of Isaac’s birth.


We have more stories about Abraham and Sarah than about any other biblical marriage. It is a different time and place, no doubt about that, but in many ways, things have not changed that much in 4,000 years. That’s how it sounds to me. It is valuable just to study this particular relationship, the Abraham and Sarah story. Most prominent marriage in the Bible.

Let’s remember Hagar’s response to God. “You are the God who sees me.” Her big surprise was not that she should go back to Sarah, or that God would take care of her.

Her big surprise was that God was watching her at all. On a dark day, say to God, “You are the God who sees me.” Say it on bright days and dark days.

Is anything too hard for God? No. What is Hagar supposed to do with a God who sees her? Go back and submit to your master. That’s what God who sees and who can do anything told Hagar.

God can take a long time to keep a promise. Far longer than is wise, in our opinion. But he keeps his promise. “I will make of you a great nation.” It turns out God did mean that, just as he said it.

But the most important lesson of this long story is something else. We say, the OT teaches, that God chose one nation, Israel, and through that nation, God blessed all the nations.

That it true, but it is the second half the story. The first half of the story is that God had to begin by creating a nation out of nothing. God began with an old couple, Abe and Sarah, old and never could have children. He chooses them when they’re so old it’s pretty much already too late to start. Then he waits another 25 years.

There should not have been any nation to choose. But God created one child where there should not be one, and then worked with that.

And not only could Sarah not conceive, neither could Rebekah, her daughter in law, Isaac’s wife. Rebekah could not conceive, so Isaac prayed to the Lord, because she could not have children. And the Lord answered his prayer, and Rebekah became pregnant. 25:21

Two generations in a row, there should not have been a nation for God to choose. And it happens also with Leah and Rachel, the wives of Abraham’s grandson Jacob. Both of them are unable to have children, until God intervenes. 29:31; 30:17, 22. Every patriarchal wife was unable to conceive until God acted.

The line God blessed should have ended three generations in a row.  God wants it clear that this nation that brings his blessing to all nations is all his doing. It is not about Israel, it is about God working with people who just can’t make it happen. So he does. Amen.

PRAYER: O God of Abraham, Sarah, and Hagar, O God who sees me, we praise you together. Hagar was a nobody, she was mistreated, she had brought this on herself in some ways, she was cut off and alone. But you were watching, and you showed up, and took care of her. You are inviting each one of us to give you that name, “the God who sees me.” Thank you for telling us this one more time.

Thank you for this rich story of Abraham and Sarah and Hagar. It is all so human, they are famous but such real and ordinary people, and yet you were faithful to them, and your purposes happened, just like you intended. I love that, please carry on like that with each of us.

And God, you wanted to bless all the nations through one nation. You began with a childless couple who trusted you most of the time. You work with people who have faith but just can’t make it happen. We give you our praise and worship. Thank you for Jesus our Lord, the center of your blessing on the nations, and for bringing us into this most fortunate line. Amen.

BENEDICTION: May the God who gives endurance and encouragement give us the same attitude of mind toward each other that Christ Jesus had, so that with one mind and one voice we may glorify the God and Father of our Lord Jesus Christ. Amen. Go in God’s peace to love and serve the Lord.