הַנְּזִירוּת הוּא נֵדֶר מִכְּלַל נִדְרֵי אִסָּר שֶׁנֶּאֱמַר (במדבר ו ב) "כִּי יִדֹּר נֶדֶר נָזִיר" וְגוֹ'. וּמִצְוַת עֲשֵׂה שֶׁיְּגַדֵּל שְׂעַר רֹאשׁוֹ שֶׁנֶּאֱמַר (במדבר ו ה) "גַּדֵּל פֶּרַע שְׂעַר רֹאשׁוֹ". וְאִם גִּלֵּחַ בִּימֵי נִזְרוֹ עוֹבֵר בְּלֹא תַּעֲשֶׂה שֶׁנֶּאֱמַר (במדבר ו ה) "תַּעַר לֹא יַעֲבֹר עַל רֹאשׁוֹ". וְכֵן אָסוּר לְהִטָּמֵא לַמֵּתִים אוֹ לֶאֱכל דְּבָרִים שֶׁאֲסָרָן הַכָּתוּב עָלָיו (במדבר ו ד) "מִגֶּפֶן הַיַּיִן" (במדבר ו ד) (במדבר ו ח) "כָּל יְמֵי נִזְרוֹ":
A nazirite vow is one of the types of vows involving prohibitions,as [Numbers 6:2] states: "When one will take a nazirite vow...." It is a positive commandment for [a nazirite] to let the hair of his head grow, as [ibid.:5] states: "He shall let the mane of the hair of his head grow." If he cuts [his hair] in the midst of the days of his nazirite vow, he violates a negative commandment, as [ibid.] states: "A razor shall not pass over his head." Similarly, he is forbidden to contract ritual impurity from a corpse or eat those products of a grape vine which the Torah forbids him from eating throughout the entire span of his nazirite vow.
