Reference: Al-Ajwibah al-Jaabiriyyah ‘alaa As.ilah al-Bareediyyah al-Iliktroniyyah – Question 2, Saturday 20 Rajab 1428AH
Question: What is the ruling regarding that which some people refer to as ‘oral sex’?
Response: Allaah has not permitted [sexual] intercourse for the man with his wife using the mouth (oral sex), never!
And none pursues this path other than the one who does not have any upright moral character, even if he is (happens to be) from amongst the Muslims; And that which is apparent is they (the Muslims) have taken this [habit] from the disbelievers through [watching] pornographic films.
So that which is obligatory upon the Muslim woman is not to allow her husband to do this.