Then the LORD did exactly what he had promised.
Sarah became pregnant, and she gave a son to Abraham in his old age. It all happened at the time God had said it would.
And Abraham named his son Isaac.
References for Genesis 21:3
Eight days after Isaac was born, Abraham circumcised him as God had commanded.
Abraham was one hundred years old at the time.
And Sarah declared, "God has brought me laughter! All who hear about this will laugh with me.