Does the captive woman immediately become an Umm Walad (mother of his child) in this scenario?
General Chapter
Al-Mughni
Book of Jihad
Primary text
The woman immediately becomes an Umm Walad to him. This is because the sexual act resulted in establishing lineage due to the semblance of ownership, thus making her an Umm Walad, similar to the captive slave of his son. The opposing views fail because ownership in the spoils is established immediately upon capture.
Supporting text
Al-Shafi'i holds that she does not become an Umm Walad immediately because she is not fully his property. There are two opinions on whether she becomes one later if he acquires full ownership. The opposing argument suggesting the rule is invalid is rejected because ownership in the spoils is established upon capture.