Answer
Wa `alaykum As-Salamu waRahmatullahi 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:
There is nothing in Islam that categorically forbids married couples from gratifying each other through oral stimulation if it is based on consensual agreement.
Answering your question, Sheikh Ahmad Kutty, a Senior Lecturer and an Islamic Scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
There is nothing in Islam that categorically forbids married couples from gratifying each other through oral stimulation if it is based on consensual agreement.
However, one objection that could be raised is whether the act involves consuming semen or female fluids, since they are considered najas (impure) according to Imam Abu Hanifah.
It is to be noted, however, that this view is not shared by other imams such as Imam Ash-Shafi`i.
The ruling that married couples are permitted to satisfy each other in this way is stated in one of the standard textbooks of the Shafi`i school of jurisprudence entitled Fath al-Mu`in, where oral stimulation of clitoris is mentioned as a permissible form of gratification among married couples. It can be further stated that there is no reason to restrict the permission to the case of males performing oral stimulation on females.
Allah Almighty knows best.