Ezekiel 44:19-20

When the priests went into the outer court they would first have to change their clothes in the rooms designated for that purpose (Ezekiel 42:1-14) so they would not transmit what was holy to what was common (cf. Leviticus 6:11). Contact with holy things consecrated those things and brought them under the restrictions governing holy things (cf. Exodus 29:37; Exodus 30:29; Leviticus 6:27; Haggai 2:12). They were also to keep their hair trimmed, not let it grow long or shave it all off. Long hair signified mourning, and pagan, idolatrous priests used to shave all their hair off as a sign of mourning (cf. Leviticus 10:6; Leviticus 21:5-6; Leviticus 21:10).