The Name Change and the Covenant Sign

Thirteen years have passed since Ishmael's birth. Abram is now ninety-nine years old. During those thirteen years, the text records nothing from God. Silence. Then God appears and speaks again: "I am God Almighty; walk before me, and be blameless, that I may make my covenant between me and you, and may multiply you greatly."

Then God changes his name:

"No longer shall your name be called Abram, but your name shall be Abraham, for I have made you the father of a multitude of nations." — Genesis 17:5 (ESV)

The name change is covenant theology in narrative form. Calvin has emphasized that identity is received from God's word, not self-constructed. Abram becomes Abraham — "father of a multitude" — because God declares it. The name embodies the promise. He walks around with a new name that describes something that does not exist yet. He is ninety-nine years old. He has one son by a slave woman. And God calls him father of a multitude of nations. We think that's what God does: He calls things that are not as though they are. He speaks the future into the present and invites the person to live into it.

Sarai is renamed Sarah. The text does not give an elaborate etymology for her name the way it does for Abraham, but God says directly: "I will bless her, and moreover, I will give you a son by her." Her new name is part of the same movement — her identity is being reshaped by what God is about to do through her.

God also institutes circumcision as a covenant sign:

"Every male among you shall be circumcised. You shall be circumcised in the flesh of your foreskins, and it shall be a sign of the covenant between me and you." — Genesis 17:10–11 (ESV)

The sign is physical and permanent. It is cut into the body. The command extends beyond Abraham himself — it covers sons, and every male servant bought with money, whether born in the household or foreign. Every male who is part of Abraham's household is to be circumcised. The covenant is not just Abraham's private matter; it shapes the whole community around him.

And then the text tells us what actually happened: Abraham was ninety-nine years old when he circumcised himself. Ishmael was thirteen. Every male in the household was circumcised that same day. The text gives us the specific ages precisely so we understand exactly how concrete and costly this act of obedience was. Abraham did not defer this. He obeyed the same day God spoke to him. The circumcision is whole-household covenant — servants included, Ishmael included — carried out immediately by a ninety-nine-year-old man who had just received this command for the first time.

Sarah and Isaac — and Abraham's Laughter

Sarai is renamed Sarah. And then God says plainly: "I will bless her, and moreover, I will give you a son by her. I will bless her, and she shall become nations; kings of peoples shall come from her."

Abraham's response is not reverent silence. He falls on his face — but he laughs. The text says: "Abraham fell on his face and laughed and said to himself, 'Shall a child be born to a man who is a hundred years old? Shall Sarah, who is ninety years old, bear a child?'"

This is worth pausing on. Abraham laughs too. Not just Sarah. Abraham, the great man of faith, falls on his face and laughs at the biological impossibility of what God is saying. We will hear more about Sarah's laughter at Mamre, but let the record show that Abraham's first reaction to hearing he will have a son with Sarah is to laugh in private disbelief.

Then he asks aloud: "Oh that Ishmael might live before you!" He is asking whether Ishmael, the son born to Hagar, might be the covenant heir. He has raised this boy for thirteen years. He loves him. He is already here. Can't the promise run through him?

God responds: "No, but Sarah your wife shall bear you a son, and you shall call his name Isaac." Then God adds the promise for Ishmael: He will bless him, make him fruitful, multiply him greatly, and make him into a great nation. Twelve princes will come from him. But — and the word is clear — "I will establish my covenant with Isaac, whom Sarah shall bear to you at this time next year."

The covenant runs through Isaac. God's mercy extends to Ishmael. Both are true. God hears the love Abraham has for Ishmael and blesses him — but the covenant heir has been designated from the beginning, and it is not Ishmael.

The Visitors at Mamre

At the oaks of Mamre, in the heat of the day, Abraham sees three visitors approaching. He runs to meet them — a ninety-nine-year-old man running in the midday heat to welcome strangers. He bows to the ground, calls himself their servant, and urges them not to pass by. He offers water for their feet and rest under the tree, then rushes to the tent to organize a meal that would have been substantial by any measure: fine flour bread, a calf — chosen, prepared, and served quickly — curds and milk. He stands by them under the tree while they eat.

During the meal, the visitors ask: "Where is Sarah your wife?" Abraham says: "She is in the tent." And then one of them says: "I will surely return to you about this time next year, and Sarah your wife shall have a son."

Sarah hears this from inside the tent. She laughs internally — to herself, privately. The text gives us her interior thought: "After I am worn out, and my lord is old, shall I have pleasure?" This is not irreverence. This is an honest response from a woman who has been barren her entire life, who has waited decades for a promise, and who is now — by any biological measure — far past the point where this could happen. She laughs because the announcement is, from where she is standing, absurd.

Then one of the visitors asks: "Why did Sarah laugh and say, 'Shall I indeed bear a child, now that I am old?' Is anything too hard for the Lord?"

He knew what she was thinking. She had laughed to herself, inside the tent. And he heard it, or knew it, and he named it. And then Sarah is afraid and denies it: "I did not laugh." But the visitor says: "No, but you did laugh."

This question — "Is anything too hard for the Lord?" — becomes one of the hinge questions of Scripture. Protestant commentators like Matthew Henry and John Calvin have highlighted Abraham's hospitality in Genesis 18 as a picture of covenant faith lived in ordinary practices: welcoming strangers, practicing generosity, keeping the household aligned with God's purposes. The scene also presents revelation: God comes to Abraham in the form of visitors, and the promise is confirmed face-to-face.

The laughter itself — both Abraham's and Sarah's — is not erased by the text. God does not pretend it didn't happen. He names it. But the question that follows isn't a rebuke exactly. It is an invitation to look at God rather than at the biological facts. Sarah laughed in disbelief. But the promise will be fulfilled. The same woman who laughed at impossibility will name her son Isaac — which means laughter. God will turn the laugh.

We don't think laughter and faith are opposites here. We think Abraham and Sarah are somewhere in between — believing and disbelieving at the same time, trusting and finding it absurd at the same time. That is where most of us live most of the time. And God meets them there. Not with judgment. With a question: Is anything too hard for the Lord?

Last updated: March 3, 2026.

Scripture quotations are from the ESV® Bible (The Holy Bible, English Standard Version®), © 2001 by Crossway, a publishing ministry of Good News Publishers.