Acharei Mot, Chapter 8
1) (Vayikra 16:30) ("For on this day He shall atone for you to cleanse you of all of your sins; before the L–rd you shall be clean.") "For on this day He shall atone for you": by the offerings. And whence is it derived that even without offerings and without the he-goat, the day (itself) atones? From "For on this day He shall atone." For transgressions between man and G d Yom Kippur atones; for transgressions between man and his neighbor Yom Kippur does not atone until he conciliates his neighbor.