Babylonian Talmud, Shabbat 65a-b

Abbahu d’Shmuel . . . did not let permit [his daughters] to lie down together. Might this be a support for R. Huna, who says that women who rub with each other are disqualified for the priesthood [i.e., marriage to a priest]? No. He held that they should not become accustomed to [sleeping with] an alien body. [Translation by Rabbi Steven Greenberg]