Mishnah Negaim 7:5: Someone who had a Baheret and it was cut off, he is pure. If he cut it off intentionally, Rabbi Eliezer says: When he gets another Nega and becomes pure from it. But the Sages say: [He is impure] until it spreads all over him. If [the Nega] was on the tip of his foreskin, he should [still] circumcise [himself].

מִי שֶׁהָיְתָה בוֹ בַהֶרֶת וְנִקְצְצָה, טְהוֹרָה. קְצָצָהּ מִתְכַּוֵּן, רַבִּי אֱלִיעֶזֶר אוֹמֵר, לִכְשֶׁיִּוָּלֶד לוֹ נֶגַע אַחֵר וְיִטְהַר מִמֶּנּוּ. וַחֲכָמִים אוֹמְרִים, עַד שֶׁתִּפְרַח בְּכֻלּוֹ. הָיְתָה בְרֹאשׁ הָעָרְלָה, יִמֹּל:

Mishnah Negaim 8:1: [If a Nega (diseased patch on skin, clothes, or houses that creates impurity) completely] spreads over the impure [body], it becomes pure. [If] the tips of the limbs return [from being covered], it becomes impure until his Baheret [type of diseased patch that creates impurity] diminishes to less than [the size of] a bean. [If it spread over] the pure [body], it becomes impure. [If] the tips of the limbs return [from being covered], it becomes impure until his Baheret returns to what it was.

הַפּוֹרֵחַ מִן הַטָּמֵא, טָהוֹר. חָזְרוּ בוֹ רָאשֵׁי אֵבָרִים, טָמֵא, עַד שֶׁתִּתְמַעֵט בַּהַרְתּוֹ מִכַּגְּרִיס. מִן הַטָּהוֹר, טָמֵא. חָזְרוּ בוֹ רָאשֵׁי אֵבָרִים, טָמֵא, עַד שֶׁתַּחֲזֹר בַּהַרְתּוֹ לִכְמוֹת שֶׁהָיְתָה: