Thematic Bible: Concubines might be dismissed

And Sarah saw the son of Hagar the Egyptian, whom she had borne to Abraham, mocking. And she said to Abraham, Cast out this handmaid and her son; for the son of this handmaid shall not inherit with my son with Isaac. And the thing was very grievous in Abraham's sight because of his son. read more.
And God said to Abraham, Let it not be grievous in thy sight because of the lad and because of thy handmaid: in all that Sarah hath said to thee hearken to her voice, for in Isaac shall a seed be called to thee. But also the son of the handmaid will I make a nation, because he is thy seed. And Abraham rose up early in the morning, and took bread, and a flask of water, and gave it to Hagar, putting it on her shoulder and the child, and sent her away. And she departed, and wandered about in the wilderness of Beer-sheba.