Answered by Shaykh Amjad Rasheed
Is it permissible for a man to suck his wife’s breast and to drink her milk?
It is permissible for a man to enjoy the whole of his wife’s body even that which is mentioned in the question, and it is permissible to drink her milk.
However, contrary to what some wrongfully understand, the rulings of suckling [s. rulings pertaining to two marriageable people becoming unmarriageable to each other due to suckling] do not apply in this case, because those rulings only apply to children who haven’t yet reached two lunar years of age.