Matthew Poole and continuators on Numbers 6:5

5 All the dayes of the vow of his separation, there shall no rasor come upon his head, untill the dayes be fulfilled, in the which he separateth himself unto the LORD, he shall be holy ; and shall let the locks of the hair of his head grow.

Nor scissers, or other instrument to cut off any part of his hair. This was appointed, partly as a sign of his mortification to wordly delights and vain affectation of outward beauty, which is promoted by the polling or cutting off the hair; partly as a testimony of that purity which hereby he professed, because the cutting off the hair was a sign of uncleanness, as appears from ver. 9. and Levit. 14. 8, 9. partly that by the notorious length of his hair he might be constantly minded of his vow and the exquisite holiness it required, and that others might thereby be admonished and stirred up to the imitation of his holy example; and partly that he might reserve his hair entirely for God to whom it was to be offered, ver. 18.

(i. e.) Wholly consecrated to God and his service, whereby he shews that inward and substantial holiness was the great thing which God required and valued in these, and consequently in other rites and ceremonies.

Marginal references: Judg. 13. 5. 1 Sam. 1. 11.