Does a husband's assault on their daughters render his wife divorced from him?

If the transgression was adultery (zina), scholars differ on whether the wife becomes forbidden to her husband if he commits adultery with her mother or daughter. The Hanafis and Hanbalis believe that unlawful sexual intercourse (al-wat' al-haram) prohibits what is lawful (al-halal), thus the mother of the woman with whom adultery was committed becomes forbidden to him. The Malikis and Shafi'is, however, believe that unlawful sexual intercourse does not prohibit what is lawful, and this is the more preponderant opinion, because the Quran forbade the mothers of wives, not the mothers of women with whom adultery was committed. Therefore, you are not divorced from your husband because of his adultery with your daughter.

If the transgression was less than adultery, then you must keep your daughters away from him. Your husband must repent from this major sin, especially if the adultery was committed with a mahram (a close relative with whom marriage is forbidden).