הלכה על שבת 207:8

However the man that is a nazirite to God is holy to God all the days of his nazirite vows and - as the verse attests to him (Numbers 6:7) - "as the crown of his God is upon him," he will not become impurified with worldly desires, and he will not be found at parties and the banquets of his companions. As his separation from wine shows about him that he has given his heart to prepare himself and to afflict himself before God, to improve the ways of his soul and to leave the pleasures of the benighted body. And since he has placed all of his heart and all of his thoughts towards his dear soul and he has abandoned all of his own needs and those of his flesh, what would be his desire for the drawing close of his companions and his friends - besides for the commandment, without a doubt. As with the raising of the soul, the pleasures of the body and all of its matters become very light in its eyes. All the more so will it not seek the company of other bodies, whether they be relatives or [others], and it will not find delight in any of their things, besides the holy service to which it is connected and to which its eyes are always directed. And hence from his great holiness and separation from his brothers, the Torah prevents him from becoming impure for them. And [it is] like the matter of the high priest - as since his matters are very elevated and he is separated from the company of his friends, and his pursuits and thoughts are only about the service of his God, may He be blessed, the Torah prevents him from becoming impure for anyone of his relatives. And the stated explanation for his distancing from impurity is also stated about the nazirite; except that with the priest, it mentions oil, since he is anointed with it, but with the nazirite, it does not mention oil. As with the priest, it states (Leviticus 21:22), "as the crown of the anointing oil of his God is upon him." But with the nazirite, it [only] states, "as the crown of his God is upon him." And maybe you will think to respond to me, that when a temporary nazirite finishes his time, he will return to his obliviousness and chase after his desires; and, if so, why should he be more stringent than a regular priest? The answer is that after a person takes on being a nazirite one time, there is hope for him to sanctify himself and to add to his goodness each day. And he will be agreed to from the Heavens and like the matter that they, may their memory be blessed, said (Shabbat 104a), "One who comes to purify himself, is assisted." And since he has taken on being a nazirite even one day, he is assisted and will finish all of his days in purity.