According to most interpretations, authorization for the husband to physically beat disobedient wives is given in the Qur'an. First, admonishment is verbal, and secondly a period of refraining from intimate relations. Finally, if the husband deems the situation appropriate, he may hit her:
"Men are the protectors and maintainers of women, because Allah has given the one more (strength) than the other, and because they support them from their means. Therefore the righteous women are devoutly obedient, and guard in (the husband's) absence what Allah would have them guard. As to those women on whose part ye fear disloyalty and ill-conduct, admonish them (first), (Next), refuse to share their beds, (And last) beat them (lightly); but if they return to obedience, seek not against them Means (of annoyance): For Allah is Most High, great (above you all)." (Qur'an 4:34 English translation: Yusuf Ali)
The medieval jurist ash-Shafi'i, founder of one of the main schools of fiqh, commented on this verse that "hitting is permitted, but not hitting is preferable."