Is it permissible for a husband to enter his co-wife's quarters during her designated time?
General Chapter
Al-Mughni
Book of the Wedding Feast
Primary text
Entering the co-wife's quarters during her time is not permitted except out of necessity (darurah), such as if the husband is a guest there, the wife made a bequest to him, or for some unavoidable matter. If the entry is due to necessity and the husband departs quickly without staying long, he does not owe the wife compensation from his following night. If he stays and the sick wife recovers, he owes the other wife compensation from her allotted time equal to the duration he stayed with the first. If he leaves for a non-necessary reason, he must complete the night with the first wife. The ruling for compensation applies similarly if he entered for necessity and stayed, as compensating a small duration offers no benefit.
Supporting text
If the husband has intercourse during a brief stay, there are two opinions: one view holds that no compensation is due because coitus is not deserved in the time allocated, and minor time is not compensated. The second view holds that he must compensate because by entering the wronged wife's dwelling on the night of intercourse and having intercourse, he balances between them, and minor time coupled with intercourse achieves tranquility (sakan), thus resembling a long stay.