כל נדרי תשפ"ג

(18) He has turned to the prayer of the destitute^-c
and has not spurned their prayer.

A sin-offering, which atones for unwitting performance of transgressions punishable by karet, and a definite guilt-offering, which is brought for robbery and misuse of consecrated items, atone for those sins. Death and Yom Kippur atone for sins when accompanied by repentance. Repentance itself atones for minor transgressions, for both positive mitzvot and negative mitzvot. And repentance places punishment for severe transgressions in abeyance until Yom Kippur comes and completely atones for the transgression.

At present, when the Temple does not exist and there is no altar of atonement, there remains nothing else aside from Teshuvah.
Teshuvah atones for all sins. Even a person who was wicked his whole life and repented in his final moments will not be reminded of any aspect of his wickedness as [Ezekiel 33:12] states "the wickedness of the evil one will not cause him to stumble on the day he repents his wickedness."
The essence of Yom Kippur atones for those who repent as [Leviticus 16:30] states: "This day will atone for you."

The commandment of resting from work on Yom Kippur: To rest from all work on Yom Kippur, as it is stated, (Leviticus 23:32), "A Shabbat of shabbaton is it to you." And I have written what they, may their memory be blessed, said (Shabbat 25a), "This 'shabbaton' is a positive commandment" - meaning to say that its understanding is as if it says, "Rest on this day."

It is from the roots of the commandment from the angle of the simple understanding [that it is] so that we not be preoccupied with anything, and [so] place all of our thoughts and all of our intent to request pardon and forgiveness from the Master of all on that day, which is prepared for the forgiveness of iniquities from the day that the world was created - and as I have written in Achrei Mot in the commandment of the service of Yom Kippur (Sefer HaChinukh 185).

He said to him: These are matters of utmost importance, exalted, i.e., mitzvot or prayer, which people nonetheless treat with contempt, vileness among the sons of men.

§ The Gemara cites a series of questions that Rava asked Rabba bar Mari, the first one being related to the previous topic of discussion. Rava said to Rabba bar Mari: From where is this matter derived whereby the Sages stated: Anyone who asks for compassion from Heaven on behalf of another, and he requires compassion from Heaven concerning that same matter, he is answered first? Rabba bar Mari said to him that the source for this is as it is written: “And the Lord changed the fortune of Job, when he prayed for his friends” (Job 42:10).