John Calvin Commentary Numbers 6:5

"All the days of his vow of separation there shall no razor come upon his head: until the days be fulfilled, in which he separateth himself unto Jehovah, he shall be holy; he shall let the locks of the hair of his head grow long." — Numbers 6:5 (ASV)

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 visible mark of their consecration, they might be continually reminded of their vow. Some think that it was a mark of honor, as if they wore a crown on their heads. In this the Popish clergy are more than ridiculous, comparing themselves to the Nazarites by their circular tonsure.³³⁴

But this reason satisfies me: that God would constantly discipline them in the faithful performance of their vow by this visible sign. It is a mark of manhood to cut the hair, and this, as Paul says, a natural feeling dictates (1 Corinthians 11:14). Therefore, the dedication of the Nazarites was shown conspicuously by their heads, so that they would not fail in their own vows through carelessness or forgetfulness.

A question arises regarding women, for whom this command appears superfluous. But this is easily answered: they were also bound to let their hair grow, so as to have it long not only from custom but in accordance with their vow. Yet there will be nothing absurd in the synecdoche, by which what is said of both sexes applies only to males.

Here also the devil formerly played his game, when he persuaded certain monks, as Augustine relates,³³⁵ to make a show of sanctity by wearing long hair. For, so that the celibacy which they had vowed might be more conspicuous, they would not allow themselves to be men, having made themselves eunuchs for the kingdom of heaven’s sake (Matthew 19:12); and, therefore, their long hair was a sign of their virginity. This example teaches us to beware of the wiles of Satan, so that our κακοζηλία does not make us apes rather than imitators of the ancients.

³³⁴ “Sous l’ombre de la couronne, qu’ils appellent, quand ils ne sont pas rasez par les bors;” with reference to the crown, as they call it, when their heads are not shaved round the edges —as they call it, when their heads are not shaved round the edges — Fr.

³³⁵ De opere Monachorum, 40. (Edit. Benedict. t. 6:501.) “Jam illud, si dici potest, quam luctuose ridiculum est, quod rursus invenerunt ad defensionem crinium suorum. Virum, inquiunt, prohibuit Apostolus habere comam; qui autem se ipsos castraverunt propter regnum coelorum, jam non sunt viri. O dementiam singularem! etc.”