First of all, it should be clear that masturbation is generally considered forbidden in Islam since it is deemed to fall under the category of sexual satisfaction outside the framework of marriage. However, mutual masturbation between the man and his wife is not haram; rather, it is permissible because it is a part of the enjoyment which Allah has allowed. Allah Almighty says: “Those who guard their chastity (i.e., private parts from illegal sexual acts). Except from their wives or (the captives and slaves) that their right hands possess,—for them, they are free from blame.” (Al-Mu’minun: 5-6)
Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
“We are not allowed to engage in sexual intercourse with our wives during their menstrual period. However, there is no taboo on gaining sexual satisfaction from them through other ways. The Prophet (peace and blessings be upon him) was once asked, “What is allowed for a husband from his wife during menstruation?” He replied, “Everything except sexual intercourse.” Just as there is no taboo on intimate touching, fondling, caressing, et cetera, there is no prohibition on spouses masturbating each other, et cetera.
Although you are not allowed to masturbate yourself, his wife can masturbate him [and vice versa] without incurring any sin. So satisfy yourself through halal (lawful) ways; we have sufficiency in what Allah has made halal for us so that we do not need to turn to that which is considered as haram (unlawful).”
Given the above, it becomes clear that while the wife is in her menses, spouses are allowed to masturbate each other.