Genesis 21:6-10

And Sarah said, God hath made me to laugh; every one that heareth will laugh with me. And she said, Who would have said unto Abraham, that Sarah should give children suck? for I have borne him a son in his old age. And the child grew, and was weaned: and Abraham made a great feast on the day that Isaac was weaned. And Sarah saw the son of Hagar the Egyptian, whom she had borne unto Abraham, mocking. Wherefore she said unto Abraham, Cast out this handmaid and her son: for the son of this handmaid shall not be heir with my son, even with Isaac.