Does mortgaging one of two related women permit intercourse with the other?
Chapter on What is Prohibited to Marry and Combining Between Them and Other Matters
Al-Mughni
Book of Marriage
Primary text
If a man mortgages one of two related women, her sister does not become lawful for him. The prohibition exists because the impediment to intercourse is due to the right of the pledgee, not because the mortgaged woman is permanently unlawful for him. Intercourse becomes permissible if the pledgee grants permission, as he possesses the ability to redeem her and regain full control whenever he wishes.