Musannaf Ibn Abi Shayba 9:1022

Ghundar narrated to us, from Sulayman, from Hisham ibn Urwah, from Asim ibn al-Mundhir, who said: I asked Urwah about His saying: "The fornicator does not marry except a fornicatress or a polytheist." He said: They were prostitute women in the pre-Islamic era who had flags by which they were known.