For the entire period of his vow of separation, no razor shall touch 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.
5. There shall no razor come upon his head. It cannot be certainly determined why God would have the Nazarites let their hair grow, except that by this present mark of their consecration, they might be more and more reminded of their vow. Some think that it was a mark of honor, as if they wore a crown on their heads.
After the law for the discovery and shame of those that by sin had made themselves vile, fitly follows this for the direction and encouragement of those who by their eminent piety and devotion had made themselves honourable, and distinguished themselves from their neighbours.
Commenting on Numbers 6:1-21
All the days of the vow of his separation,.... Be the time he has vowed to be a Nazarite a week, a, month, or more, even a thousand days, but not less than thirty, as Ben Gersom observes: there shall no razor come upon his head; he might not shave his beard, nor cut off his locks, and shave his head, nor cut short his...