The birth of Isaac

Ge 21:1: And the LORD visited Sarah as he had said, and the LORD did unto Sarah as he had spoken.
Ge 21:2: For Sarah conceived, and bare Abraham a son in his old age, at the set time of which God had spoken to him.
Ge 21:3: And Abraham called the name of his son that was born unto him, whom Sarah bare to him, Isaac.
Ge 21:4: And Abraham circumcised his son Isaac being eight days old, as God had commanded him.
Ge 21:5: And Abraham was an hundred years old, when his son Isaac was born unto him.
Ge 21:6: And Sarah said, God hath made me to laugh, so that all that hear will laugh with me.
Ge 21:7: 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.
Ge 21:8: And the child grew, and was weaned: and Abraham made a great feast the same day that Isaac was weaned.