Leviticus 21:11-12

He must not go into a house where there is a dead body. He must not make himself unclean, even if it is for his own father or mother. The high priest must not go out of the Holy Place, because if he does and becomes unclean, he will make God’s Holy Place unclean. The special oil used in appointing priests was poured on his head to separate him from the rest of the people. I am the LORD.