Sforno on Leviticus 16:29/ספורנו על ויקרא ט״ז:כ״ט

1לחקת עולם, even though G’d had provided a Temple wherein to perform the ritual called עבודה, sacrificial service, the Day of Atonement, in order to be fully effective, also requires that each person abstain from the kind of work forbidden on every Sabbath, as well as that he abstain from eating and drinking, i.e. עינוי.