Genesis 17:17-21

17Abraham fell down so that his face touched the ground. He laughed and he said to himself, ‘I am now 100 years old. That is too old to have a son. Sarah is 90 years old, so she could never give birth to a child. That is too old to have a child.’

18So Abraham said to God, ‘I would be happy if you would bless Ishmael as my son.’

19God said to Abraham, ‘No, your wife Sarah will give birth to a son for you. You must give him the name “Isaac”. I will make my covenant with him and with his descendants for all time.

20I have heard what you want me to do for Ishmael. I will bless him. I will cause him to have many descendants. Among his descendants there will be 12 rulers. His descendants will become a great nation.

21But I will make my covenant with Isaac, not with Ishmael. At about this time next year, Sarah will give birth to your son, Isaac.’