Thematic Bible: The real heir born

And the LORD visited Sarah as he had said, and the LORD did unto Sarah as he had spoken. For Sarah conceived, and bore Abraham a son in his old age, at the set time of which God had spoken to him. And Abraham called the name of his son that was born unto him, whom Sarah bore to him, Isaac. read more.
And Abraham circumcised his son Isaac being eight days old, as God had commanded him. And Abraham was a hundred years old, when his son Isaac was born unto him. And Sarah said, God has made me to laugh, so that all that hear will laugh with me. And she said, Who would have said unto Abraham, that Sarah should have nursed children? for I have borne him a son in his old age.