Genesis 21:1-7

1 The Lord dealt with Sarah as he had said, and the Lord did for Sarah as he had promised.
2 Sarah conceived and bore Abraham a son in his old age, at the time of which God had spoken to him.
3 Abraham gave the name Isaac to his son whom Sarah bore him.
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 Now Sarah said, "God has brought laughter for me; everyone who hears will laugh with me."
7 And she said, "Who would ever have said to Abraham that Sarah would nurse children? Yet I have borne him a son in his old age."