An image of God’s forgiveness and atonement is described by the prophets: “I wipe away your sins like a cloud, your transgressions like mist.. .”
When a human being wipes away dirt or erases writing, traces remain.
When a wound in the skin heals, a scar remains in its place. God, however, wipes away sins as though wiping away a cloud.
The skies are dark and gloomy, and suddenly “a wind passes by and it is no more;” nothing remains, not a hint or a trace.
The skies are clear, as though they had always been clear and always will be.
Changing the past reality and completely removing it from the world – from space, time, and existence – is not within the power of man, the created being, but only within the power of the Creator.
Only God can determine retroactively that something did not happen, just as only He can determine that something will come into being and that something exists.
–Rabbi Adin Steinsaltz