בַּיּ֥וֹם הָרִאשׁ֖וֹן מִקְרָא־קֹ֑דֶשׁ כָּל־מְלֶ֥אכֶת עֲבֹדָ֖ה לֹ֥א תַעֲשֽׂוּ׃
On the first day shall be a holy convocation; ye shall do no manner of servile work.
Sefer HaChinukh
The commandment of resting on the first day of the holiday of Sukkot: To rest from any work which is not for the needs of food for the soul on the first day of the holiday of Sukkot, as it is stated (Leviticus 23:35), "On the first day, a holy occasion."
Sefer HaMitzvot
He prohibited doing work on the first day of the Holiday (Sukkot). And that is His saying, "you shall not do any work of labor" (Leviticus 23:35). (See Parashat Emor; Mishneh Torah, Rest on a Holiday 1.)