Genesis 21:1-7 - The Birth Of Isaac
1 And the LORD visited Sarah as he had said, and the LORD did with Sarah as he had spoken. 2 For Sarah conceived and bore Abraham a son in his old age at the set time of which God had spoken to him. 3 And Abraham called the name of his son that was born unto him, whom Sarah bore to him, Isaac. 4 And Abraham circumcised his son Isaac being eight days old as God had commanded him. 5 And Abraham was one hundred years old when his son Isaac was born unto him.
6 Then Sarah said, God has made me to laugh so that all that hear will laugh with me. 7 And she said, Who would have said unto Abraham, that Sarah should have given children suck? For I have born him a son in his old age.