Musar su Numeri 6:2

We find that he is commanded to let his hair grow and at the conclusion of the term of his vow to shave it off. There is no doubt that excessive hair or total hairlessness both deprive him of the typical appearance of a human being. Such a condition helps to minimize normal human appetites, such as greed and lust. Hair carefully coiffed, tends to reinforce such human desires. We find in Nazir 4b, that Simon the Just, who had officiated as High Priest for eighty years, stated that only once in all those years did he eat of the offering that a Nazirite who had defiled himself had been forced to offer. He relates that once a good looking young man from the South had come to him, and when asked why he had allowed his hair to look so disheveled and overgrown, the young man had told him that he had assumed the vows of a Nazirite after having had a glimpse of his reflection in the water. He found himself so good looking that he had become sexually aroused. He realized at that time that this was a ruse of the evil urge, and therefore let his hair grow wild in order to preserve his innocence and future in the Hereafter. When Simon the Just heard the reason this young man had adopted the Nazirite vows, he kissed him and said: "May there be many more like you whose motivation in adopting these vows is as commendable. Concerning the likes of you the Torah has written: איש כי יפליא לנדור נדר לה'." This is what the Torah refers to when it describes a נזיר as having נזר אלוקיו עליו, "having the crown of his G–d on his head." Such a person has entered the domain that Adam was in before he sinned, before he became a זר, when he too still wore that "crown". At that time his closeness to G–d was such that it did not require something זר, i.e. an intermediary, such as holy anointing oil. This status, however, is maintained only during the currency of his vow; afterwards the Nazirite reverts to being an ordinary mortal like the rest of us and this "crown" is withdrawn from him. He therefore has to bring certain offerings to atone for reverting to a lower level of sanctity, to the condition that Adam/Man has been in since the first sin. This, then, is the reason the Nazir has to bring sin offerings.