LEV172 The Kohen Gadol shall perform the special avodah of Yom Kippur. Out of kindness towards His creations, Hashem fixes one day of the year for atonement for their sins, provided that they repent. Were there not such a day of atonement, His creations’ sins would accumulate and after two or more years the world's guilt would be so great that the world would deserve to be destroyed. In His great wisdom, in order to keep the world in existence, Hashem provides one day a year when those who repent can gain complete atonement for their sins. Hashem set this day aside for atonement and sanctified it as such at the very beginning of time--when He created the world. After He designated this day and sanctified it for this important purpose, the day itself became vested with the power to assist in bestowing atonement. Thus, our Sages teach, “Yom Kippur atones.” That is, for certain minor sins, the day itself provides that atonement.