Genesis 17:15-19

ISV(i) 15 Sarah’s Pregnancy ForetoldGod told Abraham, “As for Sarai your wife, you are not to call her Sarai any longer, because her name is to be Sarah. 16 I will bless her. Furthermore, I will give you a son from her. I will bless her, so that nations, kings, and people will come from her.”
17 Abraham fell to the ground, laughed, and told himself, “Can a child be born to a 100-year-old man? Can a 90-year-old Sarah give birth?” 18 So Abraham responded to God, “If only Ishmael would live in constant awareness that you’re always with him!”
19 But God replied, “No, but your wife Sarah will give birth to your son, and you are to name him Isaac. I’ll confirm my covenant with him as an eternal covenant for his descendants.