Genesis 17:16-19

16I will bless her. She will give birth to a son for you. Many nations of people will be her descendants. Some of them will become kings. That is how much I will bless her!’

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.