Numbers 6:7
He shall not make himself unclean for his father, or for his mother, for his brother, or for his sister, when they die: because the consecration of his God is upon his head. He shall not make himself unclean for his father, or for his mother, for his brother, or for his sister, when they die: because the consecration of his God is upon his head.
Those set apart by the Nazirite vow were forbidden to make themselves ceremonially unclean for a dead father or mother or brother or sister. That prohibition covered both touching the body and the defilement involved in mourning for close relatives. The reason was that the consecration of God rested upon the consecrated person, with its sign upon the head. The case in view involved four men bound by this vow whose term was almost expired, who still had days of purification to fulfill and the accompanying offerings and sacrifices to present.