Genesis 21:1-8

1And Jehovah visited Sarah as he had said, and Jehovah did unto Sarah as he had spoken. 2And Sarah conceived, and bare Abraham a son in his old age, at the set time of which God had spoken to him. 3And Abraham called the name of his son that was born unto him, whom Sarah bare to him, Isaac. 4And Abraham circumcised his son Isaac when he was eight days old, as God had commanded him. 5And Abraham was a hundred years old, when his son Isaac was born unto him. 6And Sarah said, God hath made me to laugh; every one that heareth will laugh with me. 7And she said, Who would have said unto Abraham, that Sarah should give children suck? for I have borne him a son in his old age.

8And the child grew, and was weaned: and Abraham made a great feast on the day that Isaac was weaned.