פירוש על ויקרא 15:17

אשר יהיה עליו שכבת זרע, “(garments or skin) which have been splattered with semen of a human being;” even only partially; (Sifra) just as when this subject was discussed previously it referred to fresh, moist semen, so here too the Torah speaks of freshly emitted semen, not dried out semen.