Sefer HaChinuch ספר החינוך

The commandment of resting from work on Yom Kippur: To rest from all work on Yom Kippur, as it is stated, (Leviticus 23:32), “A Shabbat of shabbaton is it to you.” And I have written what they, may their memory be blessed, said (Shabbat 25a), “This ‘shabbaton’ is a positive commandment” — meaning to say that its understanding is as if it says, “Rest on this day.”

It is from the roots of the commandment from the angle of the simple understanding [that it is] so that we not be preoccupied with anything, and [so] place all of our thoughts and all of our intent to request pardon and forgiveness from the Master of all on that day, which is prepared for the forgiveness of iniquities from the day that the world was created — and as I have written in Acharei Mot in the commandment of the service of Yom Kippur (Sefer HaChinukh 185).

From the laws of the commandment is that which they, may their memory be blessed, said (Megillah 7b) that anything which is forbidden to do on Shabbat — even though it is not totally work — is forbidden on Yom Kippur. The principle of the matter is, “There is no difference between Shabbat and Yom Kippur except that volitional work on Shabbat is [punishable] with stoning, and on Yom Kippur with excision.” And nonetheless, they, may their memory be blessed, permitted to trim vegetables on Yom Kippur from [the time of] the afternoon service and onward, so that it will be found ready immediately on the evening [after it] — which is not permitted on Shabbat. But the people have become accustomed to be strict about the thing and to practice prohibition in the matter, as [on] Shabbat for everything. And the rest of its details are elucidated in Tractate Yoma.

And it is practiced in every place and at all times by males and females. And one who transgresses it and does work has violated this positive commandment, besides that he has violated a negative commandment; and as we have written, with God’s help (Sefer HaChinukh 215).