Mishnah Negaim 8:2: A Baheret like [the size of] a bean with a healthy patch of skin in it, if [the Baheret] spread over his entire [body] and afterwards the patch went away, or the patch went away and afterwards [the Baheret] spread over his entire [body], he becomes pure. If [subsequently] he develops a healthy patch of skin, he is impure. If he develops white hair, Rabbi Yehoshua declares impure but the Sages declare pure.

בַּהֶרֶת כַּגְּרִיס וּבָהּ מִחְיָה כָעֲדָשָׁה, פָּרְחָה בְכֻלּוֹ וְאַחַר כָּךְ הָלְכָה לָהּ הַמִּחְיָה, אוֹ שֶׁהָלְכָה לָהּ הַמִּחְיָה וְאַחַר כָּךְ פָּרְחָה בְכֻלּוֹ, טָהוֹר. נוֹלְדָה לוֹ מִחְיָה, טָמֵא. נוֹלַד לוֹ שֵׂעָר לָבָן, רַבִּי יְהוֹשֻׁעַ מְטַמֵּא, וַחֲכָמִים מְטַהֲרִין:

Mishnah Negaim 8:3: A Baheret with white hair in it that spread over his entire [body], even though the white hair [remains] in its place, he becomes pure. A Baheret that has expansion, if it spread over his entire [body] he becomes pure. And for all of [these cases], if the tips of his limbs return [from being covered by the Baheret], they become impure. [If] it spread over part of his [body], it becomes impure. [If] it spread over his entire [body], it becomes pure.

בַּהֶרֶת וּבָהּ שֵׂעָר לָבָן, פָּרְחָה בְכֻלּוֹ, אַף עַל פִּי שֶׁשֵּׂעָר לָבָן בִּמְקוֹמוֹ, טָהוֹר. בַּהֶרֶת וּבָהּ פִּשְׂיוֹן, פָּרְחָה בְכֻלּוֹ, טָהוֹר. וְכֻלָּן שֶׁחָזְרוּ בָהֶן רָאשֵׁי אֵבָרִים, הֲרֵי אֵלּוּ טְמֵאִין. פָּרְחָה בְמִקְצָתוֹ, טָמֵא. פָּרְחָה בְכֻלּוֹ, טָהוֹר: