Exodus 29:14 Kabbalah

וְאֶת־בְּשַׂ֤ר הַפָּר֙ וְאֶת־עֹר֣וֹ וְאֶת־פִּרְשׁ֔וֹ תִּשְׂרֹ֣ף בָּאֵ֔שׁ מִח֖וּץ לַֽמַּחֲנֶ֑ה חַטָּ֖את הֽוּא׃

But the flesh of the bullock, and its skin, and its dung, shalt thou burn with fire without the camp; it is a sin-offering.

Read kabbalistic (mystical) interpretation of Exodus 29:14: and classical mystical sources.