So Abraham rose early in the morning and took bread and a skin of water and gave them to Hagar, putting them on her shoulder, and gave her the boy, and sent her away.  And she departed and wandered about in the wilderness of Beersheba.  Gen. 21:14

In this passage, the word “wandered” has also been translated as “strayed”.  Rashi says that Hagar “strayed” back to her father’s house, idolatry.  We must remember that Hagar was an Egyptian; she was likely acquired by Abraham as a gift from Pharaoh in Genesis 12.  She would have been no stranger to idolatry while in Egypt.  As for Abraham and his household, Josephus makes much effort to tell us Abraham strived to have others in his household believe in the one true God.  Ultimately Hagar chooses a wife for Ishmael who is an Egyptian (Gen. 21:21), which leaves us to wonder how receptive she was to Abraham’s God – whom she herself experienced twice (Gen. 16:8 & 21:17).

Perhaps Hagar is a picture of one who does not receive God, despite the example of Abraham, and despite her own experience with God.  In which case we see her end is like that of Cain’s line – there is nothing further to be recorded in history (save for a comparison of slavery versus freedom in Galatians 4).  The inheritance of Isaac does not belong to Ishmael; their ways were parted instead.