In His great love for the Jewish people, God took us out of Egypt, forged an eternal covenant with us, and designated and sanctified a special day each year for us, to atone for our sins. Thus, we read: “For on this day, atonement shall be made for you to purify you of all your sins; you shall purify yourselves before the Lord” (Vayikra 16:30). Purity and atonement are from God. Without them, no matter how much a person regrets past actions, he can only improve his actions in the future, but can never annul what he did in the past. Yet God, in His abundant mercy and kindness, established the Day of Atonement and the mitzva of repentance to allow us to actually erase previous sins, transgressions, and misdeeds. Thus R. Akiva proclaims:
Fortunate are you, Israel – for before Whom do you purify yourselves and Who purifies you? Your Father in heaven, as we read: “I will sprinkle pure water upon you, and you shall be pure” (Yeḥezkel 36:25), and “God is the hope (mikveh) of Israel” (Yirmiyahu 17:13). Just as a mikveh purifies the impure, so too, God purifies Israel. (Yoma 85b)
Throughout the year, there are barriers that block the revelation of God’s light in the world. However, on Yom Kippur the gates of heaven open, and a beam of divine light shines at the roots of Jewish souls, purifying them. The elevated souls immerse themselves in this light as if it were a mikveh, and they are purified from the filth of sin.
Since atonement, in its essence, is granted by God and at His will, even when Israel does not repent, Yom Kippur illuminates their inner goodness and thus cleanses the roots of their souls. However, the sins remain, so in order to neutralize their effects, suffering is necessary. This is the purpose of suffering in this world and the next. The more people regret their sins and return to God, the more effectively Yom Kippur purifies even the ramifications of sins, rendering further suffering unnecessary. This is reflected in the central berakha in the Yom Kippur Amida:
And You, Lord our God, have lovingly given us this Yom Kippur for pardoning, forgiving, and atoning – to pardon all our iniquities – a sacred occasion commemorating the exodus from Egypt…. Our God and God of our forefathers: pardon our iniquities on this Yom Kippur; wipe away and remove all our transgressions and sins from before Your eyes, as it is said: “I, I am the One Who shall wipe away your transgressions for My sake, and I shall not recall your sins” (Yeshayahu 43:25). And it is said: “I have wiped away, like mist, your transgressions, and like a cloud, your sins; return to Me, for I have redeemed you” (ibid. 44:22). And it is said: “For on this day, atonement shall be made for you to purify you of all your sins; you shall purify yourselves before the Lord” (Vayikra 16:30). Sanctify us through Your mitzvot and grant that our lot be in Your Torah. Satisfy us with Your goodness, delight our souls with Your salvation, and purify our hearts to serve You in truth. For You are the Forgiver of Israel and the Pardoner of the tribes of Yeshurun in every generation, and without You we have no king who pardons and forgives but You. Blessed are You, Lord, King Who pardons and forgives our iniquities and those of all His people the house of Israel, and removes our guilt each year, King of all the earth, Who sanctifies Israel and Yom Kippur.