Genesis 21:1-7

The LORD cared for Sarah as he had said and did for her what he had promised. Sarah became pregnant and gave birth to a son for Abraham in his old age. Everything happened at the time God had said it would. Abraham named his son Isaac, the son Sarah gave birth to. He circumcised Isaac when he was eight days old as God had commanded. Abraham was one hundred years old when his son Isaac was born. And Sarah said, “God has made me laugh. Everyone who hears about this will laugh with me. No one thought that I would be able to have Abraham’s child, but even though Abraham is old I have given him a son.”