Midrash su Levitico 23:27

1) (Vayikra 23:27) ("Only on the tenth day of this seventh month it is the day of atonement. A holy calling shall it be for you. And you shall afflict your souls and you shall present a fire-offering to the L–rd.") "the day of atonement, a holy calling," "the day of atonement and you shall afflict your souls," (Vayikra 23:28) "And all work you shall not do for it is a day of atonement." (Why three times?) For I might think that Yom Kippur does not atone unless he made it a holy calling (in the blessings of the day), and afflicted himself, and abstained from labor. Whence do I derive that even if he did not do these, the day atones? From "It is the day of atonement." I might think that Yom Kippur atoned only with the offerings and with the he-goats. Whence do I derive that the day atones even without them? From "It is the day of atonement." I might think that it atones both for those who repent and those who do not. — No would this follow? A sin-offering and a guilt-offering atone. Just as they atone only for penitents (viz. Bamidbar 5:7), so, Yom Kippur should atone only for penitents!

2) — No, this may be so for a guilt-offering and a sin-offering, which do not atone for witting sin as for unwitting sin. Would you say the same for Yom Kippur, which does atone for witting as for unwitting sin? And since it does, we would say that it atones both for those who do repent and for those who do not. It is, therefore, written "Only" (a term of exclusion). To teach that it atones only for those who repent.

8) And whence is it derived that if Yom Kippur fell on a Sabbath and he unwittingly performed a (forbidden) labor that he is liable for each (day) in itself? From "It is Sabbath," (Vayikra 23:27) "It is Yom Kippur." These are the words of R. Akiva. R. Yossi says: He is liable only for one.