Talk to My Lawyer

The Ancient Near Eastern context of this story suggests that conflict over inheritance rights precipitated Sarah's request that Hagar and Ishmael be sent away. In ancient Mesopotamian law codes (Abraham, after all, did come from the Mesopotamian city of Ur), we learn that freeing a maidservant disqualifies a son she may have borne to the master of the house from inheriting his estate.

Take the following example from the Lipit Ishtar law code, which dates from approximately 1950 B.C.E.:

If a man married a wife (and) she bore him children and those children are living, and a slave also bore children for her master (but) the father granted freedom to the slave and her children, the children of the slave shall not divide the estate with the children of their (former) master.

So when Sarah said: 'Cast out that slave-woman and her son, for the son of that slave shall not share in the inheritance with my son Isaac' (Genesis 21:10), she was simply asking Abraham to carry out a legal procedure which would cause Ishmael to forfeit his right to inheritance.