(34) On the seventh day the priest shall examine the scall. If the scall has not spread on the skin, and does not appear to go deeper than the skin, the priest shall pronounce the person pure; after washing those clothes, that person shall be pure. (35) If, however, the scall should spread on the skin after the person has been pronounced pure, (36) the priest shall conduct an examination. If the scall has spread on the skin, the priest need not look for yellow hair: the person is impure. (37) But if the scall has remained unchanged in color, and black hair has grown in it, the scall is healed; the person is pure. The priest shall pronounce that person pure.
ונתתי נגע צרעת. בְּשׂוֹרָה הִיא לָהֶם שֶׁהַנְּגָעִים בָּאִים עֲלֵיהֶם; לְפִי שֶׁהִטְמִינוּ אֱמוֹרִיִּים מַטְמוֹנִיּוֹת שֶׁל זָהָב בְּקִירוֹת בָּתֵּיהֶם כָּל אַרְבָּעִים שָׁנָה שֶׁהָיוּ יִשְֹרָאֵל בַּמִּדְבָּר, וְעַל יְדֵי הַנֶּגַע נוֹתֵץ הַבַּיִת וּמוֹצְאָן (ויקרא רבה י"ז):
ונתתי נגע צרעת [WHEN YOU COME TO THE LAND …]I WILL PUT THE PLAGUE OF THE LEPROSY — This was an announcement to them that these plagues would come upon them (Sifra, Metzora, Section 5 4; Horayot 10a), because the Amorites concealed treasures of gold in the walls of their houses during the whole 40 years the Israelites were in the wilderness (in order that these might not possess them when they conquered Palestine,) and in consequence of the plague they would pull down the house and discover them (Leviticus Rabbah 17:6).
It [tsaraath] is probably no more contagious than pulmonary consumption, and less so than syphilis. With these diseases, however, there was no biblical example of ostracism to be followed. Despite the explicit proscriptions in Leviticus, there is much evidence to prove that the ancient Jews themselves, at least in the talmudical times, did not look upon tsaraath as contagious. While Jewish lepers were obliged to live outside the camp, the same restrictions were not imposed upon non-Jews. The Mishnah says: Leprous heathens and unnaturalized proselytes were not unclean; neither were the clothing nor the houses of leprous heathens unclean...
They [lepers] had violated the laws of God, and their transgression had been great, else they would not have been so afflicted. Their presence, therefore, in the community was likely to contaminate, to morally infect others: hence were they ostracized. And so long as the signs of the disease, or, metaphorically speaking, the finger of God, remained upon them, so long were they obliged to remain without the camp. When the leper was cured, the priest was to make an atonement before the Lord, and expiatory sacrifices in the form of a sin-offering and a trespass-offering were to be made.