Answer
Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- We are not allowed to engage in sexual intercourse with our wives during their menstrual period.
2- Masturbation is generally considered forbidden in Islam since it is deemed to fall under the category of sexual satisfaction outside the framework of marriage.
3- 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.
In response to your question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
Sex during Wife’s Period
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.”
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 23:5-6)
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, your wife can masturbate you 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).
Allah Almighty knows best.
Excepted, with slight modifications, from: www.muslims.ca