Genesis 21:1-8

And the Lord visited Sara, as he had promised: and fulfilled what he had spoken. And she conceived and bore a son in her old age, at the time that God had foretold her. And Abraham called the name of his son, whom Sara bore him, Isaac. And he circumcised him the eighth day, as God had commanded him. When he was a hundred years old: for at this age of his father was Isaac born. And Sara said: God hath made a laughter for me. Whosoever shall hear of it will laugh with me. And again she said: Who would believe that Abraham should hear that Sara gave suck to a son, whom she bore to him in his old age? And the child grew and was weaned: and Abraham made a great feast on the day of his weaning.