Numbers 6:7
He may not make himself unclean for his father or his mother, his sister or his brother, if death comes to them; because he is under an oath to keep himself separate for God.
Numbers 9:6
And there were certain men who were unclean because of a dead body, so that they were not able to keep the Passover on that day; and they came before Moses and before Aaron on that day:
Leviticus 21:1-2
And the Lord said to Moses, Say to the priests, the sons of Aaron, Let no man make himself unclean for the dead among his people;
Leviticus 21:10-12
And he who is the chief priest among his brothers, on whose head the holy oil has been put, who is marked out to put on the holy robes, may not let his hair go loose or have his clothing out of order as a sign of sorrow.
Ezekiel 44:25
They are not to come near any dead person so as to become unclean: but for a father or mother or son or daughter or brother or for a sister who has no husband, they may make themselves unclean.