Reference: Fataawa Muhimmah li-Nisaa. al-Ummah – Page 146
Liqaa. al-Baab al-Maftooh – Number 12
Question: What is the rule regarding the limits for a man seeking pleasure with his wife with respect to her entire body?
Response: The rule is that he should not approach (enter) her via her anus, nor approach (enter) her via her vagina whilst she is in the state of menstruating or postpartum bleeding. This is the rule, as Allaah (Subhaanahu wa Ta’aala) says:
{And those who guard their chastity. Except from their wives or (the captives and slaves) that their right hands possess, for then, they are free from blame. But whoever seeks beyond that, then those are the transgressors}, [Soorah al-Mu.minoon, Aayaat 5-7]