Mishnayos Negaim Perek 8 Mishnah 9

פרחה בכולו ואח"כ נתגלו בו ראשי אברים – here we are speaking about [the case] that he (i.e., the Kohen) did not manage to declare him a certified leper until it had erupted/blossomed throughout all of his body and uncovered the tips of the limbs, that Rabbi Yishmael compared him to someone who comes in totally white at the outset except for the tips of the limbs, which requires isolation/quarantine/being shut up. But Rabbi Eleazar ben Azariah holds that since whereas it did not erupt/blossom, he (i.e., the Kohen) would declare him to be a certified leper, his law is like a small bright white spot on the skin which has on it quick flesh, for if it had erupted on his entire body and afterwards, the tips of the limbs were uncovered/revealed, he would be impure. And there is more to explain, that even if he had declared him a certified leper with quick flesh and it had erupted throughout all of the body and he had purified him, as Rabbi Yishmael holds, that one does not defile with the reappearance of the tops of the limbs, that one defiles with the reappearance of the tops of the limbs that is after the eruption/blossoming [which causes the leper to be declared clean], where he is pure in the practice of eruption/blossoming, but here, it is not the practice of eruption/blossoming where he is pure, for had there been a diminution of quick flesh from like the size of a lentil, he would be pure.