Salaamun Alaykum

I do not belive the exact phrase "marital rape" occurs in Islamic sources. That, however, does not mean that Islam condones rape within a marital context. 

The Quranic command is for husband and wife to live with each other honourably and kindly. A number of ahadith further put emphasis on this. Husbands are ordered to treat their wives with fairness, kindness and patience. They are not to harm them. 

As for sexual intercourse, husbands are further ordered to take care of their wives' needs and the husband is not to proceed with the actual coitus until the wife is ready.

Again, we remind ourselves that husbands are not allowed to mistreat and/or harm their wives. 

Hence, although the terminology "marital rape" does not occur in the sources (as far as I know), I believe one must conclude that the act as such is not allowed.

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