Levítico 23:28 Halachá: Sefer HaChinukh & Sefer HaMitzvot

To not do work on the tenth of Tishrei: To not do any work on Yom Kippur - and it is the tenth day of Tishrei - as it is stated (Leviticus 23:27), "on the tenth of the seventh month, etc."; and it is written after it (Leviticus 23:28), "And you shall not do any work on that very day, since it is the day of atonements, to atone for you." And the word, "since" (ki), [indicates] the giving of a reason for the cessation from work. And [it is] like the matter that I shall write later in this Order in the commandment of resting on Yom Kippur (Sefer HaChinukh 317). And you also find all of the content of this commandment there - and I will not write an addition for you about something that is not needed.

He prohibited doing work on Yom Kippur. And that is His saying, "you shall not do any work" (Leviticus 23:28). And one who transgresses this negative commandment is [punished] with excision, as is explained in Scripture. But if it was inadvertent, he is liable for a fixed sin-offering. And the regulations of this commandment have been explained in Tractate Beitzah, Megillah and other ones besides them. (See Parashat Emor; Mishneh Torah, Rest on a Holiday 1.)