Genesis 21:1-6 RSV

1 The LORD visited Sarah as he had said, and the LORD did to Sarah as he had promised.
2 And Sarah conceived, and bore Abraham a son in his old age at the time of which God had spoken to him.
3 Abraham called the name of his son who was born to him, whom Sarah bore him, Isaac.
4 And Abraham circumcised his son Isaac when he was eight days old, as God had commanded him.
5 Abraham was a hundred years old when his son Isaac was born to him.
6 And Sarah said, "God has made laughter for me; every one who hears will laugh over me."