A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
num 6:2THE LAW OF THE NAZARITE IN HIS SEPARATION. (Num. 6:1-22)
When either man or woman . . . shall vow a vow of a Nazarite--that is, "a separated one," from a Hebrew word, "to separate." It was used to designate a class of persons who, under the impulse of extraordinary piety and with a view to higher degrees of religious improvement, voluntarily renounced the occupations and pleasures of the world to dedicate themselves unreservedly to the divine service. The vow might be taken by either sex, provided they had the disposal of themselves (Num 30:4), and for a limited period--usually a month or a lifetime (Jdg 13:5; Jdg 16:17). We do not know, perhaps, the whole extent of abstinence they practised. But they separated themselves from three things in particular--namely, from wine, and all the varieties of vinous produce; from the application of a razor to their head, allowing their hair to grow; and from pollution by a dead body. The reasons of the self-restrictions are obvious. The use of wine tended to inflame the passions, intoxicate the brain, and create a taste for luxurious indulgence. The cutting off the hair being a recognized sign of uncleanness (Lev 14:8-9), its unpolled luxuriance was a symbol of the purity he professed. Besides, its extraordinary length kept him in constant remembrance of his vow, as well as stimulated others to imitate his pious example. Moreover, contact with a dead body, disqualifying for the divine service, the Nazarite carefully avoided such a cause of unfitness, and, like the high priest, did not assist at the funeral rites of his nearest relatives, preferring his duty to God to the indulgence of his strongest natural affections.
num 6:9If any man die very suddenly by him, and he hath defiled the head of his consecration--Cases of sudden death might occur to make him contract pollution; and in such circumstances he was required, after shaving his head, to make the prescribed offerings necessary for the removal of ceremonial defilement (Lev 15:13; Num 19:11). But by the terms of this law an accidental defilement vitiated the whole of his previous observances, and he was required to begin the period of his Nazaritism afresh. But even this full completion did not supersede the necessity of a sin offering at the close. Sin mingles with our best and holiest performances, and the blood of sprinkling is necessary to procure acceptance to us and our services.
num 6:13when the days of his separation are fulfilled, &c.--On the accomplishment of a limited vow of Nazaritism, Nazarites might cut their hair wherever they happened to be (Act 18:18); but the hair was to be carefully kept and brought to the door of the sanctuary. Then after the presentation of sin offerings and burnt offerings, it was put under the vessel in which the peace offerings were boiled; and the priest, taking the shoulder (Lev 7:32), when boiled, and a cake and wafer of the meat offering, put them on the hands of the Nazarites to wave before the Lord, as a token of thanksgiving, and thus released them from their vow.
num 6:23THE FORM OF BLESSING THE PEOPLE. (Num 6:23-27)
Speak unto Aaron and unto his sons, saying, On this wise ye shall bless the congregation of Israel, &c.--This passage records the solemn benediction which God appointed for dismissing the people at the close of the daily service. The repetition of the name "Lord" or "Jehovah" three times, expresses the great mystery of the Godhead--three persons, and yet one God. The expressions in the separate clauses correspond to the respective offices of the Father, to "bless and keep us"; of the Son, to be "gracious to us"; and of the Holy Ghost, to "give us peace." And because the benediction, though pronounced by the lips of a fellow man, derived its virtue, not from the priest but from God, the encouraging assurance was added, "I the Lord will bless them."