Negative commandment · Lo Ta’aseh #206 of 613
[For a Nazarite] not to eat grape peels
שלא יאכל זוגין
The verse · Bamidbar 6:4
כֹּל יְמֵי נִזְרוֹ מִכֹּל אֲשֶׁר יֵעָשֶׂה מִגֶּפֶן הַיַּיִן מֵחַרְצַנִּים וְעַד־זָג לֹא יֹאכֵל
“All the days of his abstinence shall he eat nothing that is made of the vine tree, from the kernels even to the husk.”
The Rambam’s words
[For a Nazarite] not to eat grape peels, as [Numbers, ibid.] continues: "He shall not eat [anything from wine grapes,...] to its peels."
שלא יאכל זוגין, שנאמר "ועד זג--לא יאכל" (במדבר ו,ד).
Where in the Mishneh Torah
Hilchot Nazariteship הלכות נזירות