Khuddakavatthukkhandhaka

Vinayapiṭaka · Cūḷavagga (2) · Vol. 7 · Section 154

[154] Now at that time bhikkhus wore the hairs of their nostrils long. People looked down upon them, criticized them, and spread it about, saying, "… just like demon-worshippers (pisācillikā) …" … They informed the Blessed One of this matter. "Bhikkhus, the hair of the nostrils is not to be worn long. Whoever should wear it so commits an offense of wrongdoing (dukkaṭa)."

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.

This passage also appears in 1 other place

Vol. 7 · Section 13 — Khuddakavatthukkhandhaka