I have read that Abraham gave Hagar a divorce but the source was disreputable and I could not find a reputable one.
The context here is that I am learning Iyov and thinking about the misfortunes that some must bear. The talmud says "Anyone who divorces his first wife - even the Altar sheds tears." (Gittin 90a-b)".
edit: we can ask why Iyov is afflicted/punished by one means but not another. Here I am asking why Iyov was not afflicted/punished by divorce and who was. The first question posed -- who was -- is historic, but it sets up the second question posed (what does the tradition say regarding these marriages) that is certainly Judaic/theological.