But in this post, two more bits of evidence. The first in Yeshaya 15:
The second bit of evidence is from Herodotus, father of history, or else father of lies. In The Histories 2.35-36, he writes:
Elsewhere priests grow their hair long; in Egypt they shave their heads. In other nations the relatives of the deceased in time of mourning cut their hair, but the Egyptians, who shave at all other times, mark a death by letting the hair grow both on head and chin.Note the connection specifically with the priestly caste; this accords with the pasuk in Emor singling out the kohanim, and with Rambam relating it to avodah zarah practices. But also note the connection with death, and how in many cultures, cutting the hair is a sign of mourning.