וְרָאָ֨ה אֶת־הַנֶּ֜גַע בַּיּ֣וֹם הַשְּׁבִיעִ֗י כִּֽי־פָשָׂ֤ה הַנֶּ֙גַע֙ בַּ֠בֶּגֶד אֽוֹ־בַשְּׁתִ֤י אֽוֹ־בָעֵ֙רֶב֙ א֣וֹ בָע֔וֹר לְכֹ֛ל אֲשֶׁר־יֵעָשֶׂ֥ה הָע֖וֹר לִמְלָאכָ֑ה צָרַ֧עַת מַמְאֶ֛רֶת הַנֶּ֖גַע טָמֵ֥א הֽוּא׃
And he shall look on the plague on the seventh day: if the plague be spread in the garment, or in the warp, or in the woof, or in the skin, whatever service skin is used for, the plague is a malignant leprosy: it is unclean.
Read kabbalistic (mystical) interpretation of Leviticus 13:51: and classical mystical sources.