The mitzvah onah, the mitzvah of marital sex, is defined in the mishna in Ketuvot as fixed, regular times that a husband must have sex with his wife. However, another definition emerges from other Talmudic passages – that the husband must have sex with his wife when he sees that she desires it, and this is referred to as lisameyach et ishto bi’dvar mitzvah, to give pleasure to his wife with this mitzvah act.

There is a debate in the achronim which of these two is the fundamental obligation. Rav Chaim Ozer Grodansky (Achiezer 3:83) rules that the fundamental obligation is