Genesis 21:7-11

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.

And the child grew, and was weaned: and Abraham made a great feast the same day that Isaac was weaned.

And Sarah saw the son of Hagar the Egyptian, which she had born unto Abraham, mocking.

Wherefore she said unto Abraham, Cast out this bondwoman and her son: for the son of this bondwoman shall not be heir with my son, even with Isaac.

And the thing was very grievous in Abraham’s sight because of his son.