What did God tell Abraham to do with his first son, Ishmael?

Abandon him and his mother in the wilderness.

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....

And God said unto Abraham, Let it not be grievous in thy sight because of the lad, and because of thy bondwoman; in all that Sarah hath said unto thee, hearken unto her voice. Genesis 21:9-12