Halakhah su Levitico 23:34

To not do work on the first day of the holiday of Sukkot: To not do work that is not for the needs of food for the soul on the first day of the holiday of Sukkot - which is the fifteenth of Tishrei - as it is stated (Leviticus 23:34-35), "Speak to the Children of Israel, saying, 'On the fifteenth day of the seventh month, etc. On the first day is a holy occasion; all work of labor shall you not do.'" I have written the content of the prohibition of work on the holiday, above about Pesach in this Order (Sefer HaChinukh 298); and its content is the same in everything.

It is a positive biblical commandment to sit in the Sukkah for seven days, from the 15th of Tishrei until after the 21st of Tishrei, for it is written in Parashat Emor (Leviticus 23:34): "On the fifteenth day of this seventh month is the feast of tabernacles for seven days unto the LORD... Ye shall dwell in booths seven days; all that are home-born in Israel shall dwell in booths; that your generations may know that I made the children of Israel to dwell in booths, when I brought them out of the land of Egypt" (Leviticus 23:42-43).