For the entire period of his vow of separation, no razor shall pass over his head. He must be holy until the time of his separation to the LORD is complete; he must let the hair of his head grow long.
Jewish Publication Society of America Version (JPS1917) - Numbers 6:5 >All the days of his vow of Naziriteship there shall no razor come upon his head; until the days be fulfilled, in which he consecrateth himself unto the LORD, he shall be holy, he shall let the locks of the hair of his head grow long.