Charles Ellicott Commentary 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 his separation unto God is upon his head." — Numbers 6:7 (ASV)

He shall not make himself unclean ... — The law of the Nazirite in this respect was equally stringent with that of the high priest (Leviticus 21:11), and more stringent than that which was imposed upon the priests generally (Leviticus 21:2–3).

The consecration. —Better, the separation (Hebrew, nezer). So also in Numbers 6:9.