Genesis 21:1-7

The LORD dealt with Sarah as he had said, and the LORD did for Sarah as he had promised. Sarah conceived and bore Abraham a son in his old age, at the time of which God had spoken to him. Abraham gave the name Isaac to his son whom Sarah bore him. And Abraham circumcised his son Isaac when he was eight days old, as God had commanded him. Abraham was a hundred years old when his son Isaac was born to him. Now Sarah said, “God has brought laughter for me; everyone who hears will laugh with me.” 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.”