זָב שֶׁרָאָה קֶרִי, וְנִדָּה שֶׁפָּלְטָה שִׁכְבַת זֶרַע, וְהַמְשַׁמֶּשֶׁת שֶׁרָאֲתָה נִדָּה - צְרִיכִין טְבִילָה. וְרַבִּי יְהוּדָה פּוֹטֵר.

A Zav who saw a seminal emission, a niddah who emitted semen from prior sexual relations and a woman who had marital relations that saw her niddah (period): they are required to immerse in a mikvah. However, Rabbi Yehudah exempts them [from mikvah in-order to study Torah].