Commentary for Berakhot 42:16

תנן זב שראה קרי ונדה שפלטה שכבת זרע המשמשת וראתה דם צריכין טבילה ורבי יהודה פוטר

There is a Mishnaic teaching : A man with a running issue who has experienced emission, a menstruous woman from whom the semen has escaped and a woman who during intercourse experiences the menstrual flow require immersion ; but R. Judah exempts them therefrom.

Abraham Cohen Footnotes to the English Translation of Masechet Berakhot