He shall shave his head, because his whole body, and especially his hair, was defiled by such an accident, which he ought to impute either to his own heedlessness, or at least to God's providence, so ordering the matter possibly for the punishment of his other sins, or for the quickening of him to more caution and purity, and detestation of all dead works whereby he would be defiled. On the seventh day, to be reckoned from the time of his pollution; for uncleanness contracted by the dead continued for seven days, and the seventh day was the day of cleansing for it, Leviticus 15:13 Numbers 19:11,12.
Related Commentaries of Numbers 6:9
Numbers 6:9
9 And if any man die very suddenly by him, and he hath defiled the head of his consecration; then he shall shave his head in the day of his cleansing, on the seventh day shall he shave it.