For much of Islamic history, the unit through which the Sunna was preserved, transmitted, and understood has been the hadīth (Arabic plural, ahādīth … - Jonathan A.C. Brown

No compulsion in religion’ (2:256) was a Qur'anic command revealed in Medina when a child from one of the Muslim families who had been educated in the town's Jewish schools decided to depart with the Jewish tribe being expelled from Medina. His distraught parents were told by God and the Prophet in this verse that they could not compel their son to stay. The verse, however, has been understood over the centuries as a general command that people cannot be forced to convert to Islam.

Here the Shariah historically worked differently from modern laws on marital rape, which originated in the 1970s. But the effect is similar: protection. Within marriage, wrongs regarding sex were not conceived of as violations of consent. They were conceived of as harm inflicted on the wife. And in Islamic history wives could and did go to courts to complain and get judges to order husbands to desist and pay damages. So yes, non-consensual sex is wrong and forbidden in Islam. But the operating element to punish marital rape fell under the concept of harm, not non-consent

As noted earlier, marriage and a male's ownership of a female slave were the two relationships in which sex could licitly occur according to the Shariah. In marriage, the consent of the wife to sex was assumed by virtue of the marriage contract itself. In the case of the slave-concubine, consent was irrelevant because of the master's ownership of the woman in question. As Kecia Ali has noted, there is no evidence for any requirement for consent from slave women in books of Islamic law in the formative centuries of Islam. Books of Islamic law and natural ethics are full of exhortations for husbands to enter in foreplay and stress the wife's right to orgasm. But such books also foreground Hadiths and laws obliging wives to meet their husbands' sexual needs without contest. [...] In the Shariah, consent was crucial if you belonged to a class of individuals whose consent mattered: free women and men who were adults (even male slaves could not be married off against their will according to the Hanbali and Shafiʿi schools, and this extended to slaves with mukataba arrangements in the Hanafi school). Consent did not matter for minors. And it did not matter for female slaves, who could be married off by their master or whose master could have a sexual relationship with them if he wanted (provided the woman was not married or under a contract to buy her own freedom).