Re: Relations with slave girls
Slave girls were very common in Pre-Islam Arab and in some cases they were made to do prostitution by their Masters. There are verses in Quran prohibiting this issue. Quran was revealed gradually and certain sharia rules were imposed in stages like period of iddat of a lady was not 4 months at first. There is a verse in Quran which talks of one year’s iddat (need to check).
Link in post 3 got some valid points where similarities between marriage with a free woman and relationship with a slave girl are mentioned.