Numbers 6:3

From new or old [intoxicating] wine. As Targum [Onkelos] translates; “from new wine or old”: Wine intoxicates when aged.

Anything steeped in grapes. The word [מִשְׁרַת] denotes adding color to water, or any beverage. In the Mishnaic idiom, there are many [examples]: ‘One does not steep ink or dye’, ‘If a nazirite steeped his bread in wine’.

he shall abstain from wine, new and old, he shall drink neither vinegar of old wine or new; neither may he drink liquor in which grapes have been crushed, nor eat of grapes either fresh or dried.

משרת ענבים, according to Menachem the word משרת is derived from the root שרת, as in Numbers 8,26 ושרת את אחיו, “he (the Levite) will assist his brethren (the priests) in the service, i.e. he will not be allowed to substitute for him.” The letter מ at the beginning of the word משרת would then have to be understood like the letter מ in מרמס In Isaiah 10,6 or as in the word משמר in Genesis 40,3, i.e. as a letter which converts a verb into a noun.
It is not possible to explain the word משרת as related to שרת, in the sense of assist, serve, except when it occurs in connection with service performed by human beings for their masters.
Therefore, I believe that the word משרת belongs to a category of verbs which have the peculiarity that the last letter of their root disappears when the verb (or noun derived from it) appears in the construct mode. An example is the verb קנה, acquired, or מקנה, acquisition, which when in the construct form becomes מקנת, “acquisition of.” (compare Exodus 12,44) Although this expression is not found elsewhere in the Torah it does occur in the Talmud, always referring to something which had been soaked in water, such as in Nazir 36 where it describes a Nazirite who had soaked his bread in grape juice. We also find an expression in Jeremiah 15,11אם לא שריתיך לטוב, which is explained there by Rashi as similar to Daniel 5,12 משרא, being freed form shackles. The word שריתיך in Jeremiah is understood as “I have scattered you,” if instead of with the letter ש it had been spelled with the letter ז. Compare Maleachi 2,3 where it appears as “I will strew, scatter, etc.” You will find this word in this sense in Numbers 17,2 when Eleazar is told to scatter the fire which had been on the pans on which the congregation of Korach had offered their incense. משרת ענבים in our verse also means anything which separated from the actual grapes and fell down. It is like a person after he had been freed from the chains that had held him captive.

מיין ושכר יזיר, he is not to flagellate himself, or practice fasting, but only to abstain from wine and intoxicating liquids. The former methods of self-denial would result in a diminished ability to serve the Lord with all one’s faculties. Flagellation, a common practice among certain types of monks and “holy men,” is not allowed, but becoming a teetotaler does reduce the urge to let oneself go and engage in demeaning activities due to drunkenness