Ezekiel 44:20

The priests shall poll or cut the hair of their heads, and neither shave their heads bald nor let the hair flow loose. Shaving the head bald was a sign of mourning (Leviticus 21:5; Leviticus 21:10, cf. Ezekiel 24:17), and forbidden both to priests and people as a practice of the heathen (Deuteronomy 14:1); though the prophets frequently refer to it as a token of disaster and mourning; Isaiah 3:24; Isaiah 22:12; Jeremiah 16:6; Amos 8:10; Micah 1:16; Leviticus 10:6 indicates that letting the hair flow loose and dishevelled was also a sign of grief. The phrase appears used both of this practice and of the Nazirite custom of allowing the hair to remain uncut (Numbers 6:5, cf. Numbers 5:18).