Musar su Salmi 41:78

Know and understand that the reproof of God, may He be blessed, is for the good of man. For if a man sins in front of Him and does evil in His eyes, God's reproof is upon him for two purposes: One is to atone for his sins and to remove the iniquity, as it is stated (Psalms 25:18), "Look at my affliction and suffering, and forgive all my sins." So with the sicknesses of the body, with which God has made him sick, is the sickness of the soul healed. For iniquity is the sickness of the soul, as it is stated (Psalms 41:5),"heal me, for I have sinned against You." And it is [also] stated (Isaiah 33:24), "And none who lives there shall say, 'I am sick'; It shall be inhabited by folk whose sin has been forgiven." And the second is to remind him and have him repent from his evil ways, as it is written (Zephaniah 3:7), "she would fear Me, would take reproof." But if he does not receive the reproof and does not cease on account of the rebuke and does not circumcise the covering of his heart - woe is to him and woe to his soul. For he has suffered afflictions and bore his sin, but his iniquity was not atoned; but rather his punishment was doubled, as we explained.

The differences in atonement
In the same way as the body has sicknesses and ailments, so too does the soul. And the ailments of the soul and its diseases are its evil traits and its sins. But when an evildoer repents from his evil path, God, may He be blessed, heals the soul of the sinner - as it is stated (Psalms 41:5), “O Lord, have mercy on me, heal my soul, for I have sinned against You.” And it is [also] stated (Isaiah 6:10), “and repent and save itself.” And in the way that it is sometimes found with the sicknesses of the body that the sickness lightens itself from upon one, as does the length of most of the ailments, but the body is not cleansed of it without drinking a bitter drink and suffering further by afflicting his soul from [eating] all desirable food; so too is it with the soul sick from great iniquity: And even though most of the sickness is healed, and most parts of the punishment are removed after the repentance - and God, may He be blessed, has gone away from His anger - the soul will not yet be cleansed from the sickness and its sin will not be atoned until the sinner is made to suffer with afflictions, purified with pain and with bad and difficult things that happen to him. [This is] like the matter that is stated (Genesis 4:13-14), “My punishment is too great to bear! Since You have banished me this day from the soil, and I must avoid Your presence; and I shall be a fugitive and a wanderer in the earth; and it will come to pass, that whoever finds me will kill me.” However through repentance, most of his iniquity was forgiven, the main part of his punishment was removed and he was rescued from death - as it is stated (Genesis 4:15), “and the Lord put a mark on Cain, lest anyone who met him should kill him.” But the punishment of exile remained for him, as it is stated (Genesis 4:12), “and I shall be a fugitive and a wanderer in the earth.” Yet he had mentioned [his] migration with a double expression (fugitive and wanderer); whereas after the repentance, it is [only] stated (Genesis 4:16), “and he dwelt in the land of wandering.”

The commentators have difficulty with the word כי in the verse. Rabbi Bachyah, for instance, understands the word in the same sense as it is used in such verses as סלח לנו אבינו כי חטאנו, "Forgive us our Father, although we have sinned," or as in Psalms 41,5: רפאה נפשי כי חטאתי לך, "Heal me although I have sinned against You."

And further: Another poor man came before Rabbi Yitzchak carrying a half ma’ah coin in his hand. He said to Rabbi Yitzchak, “Make my soul and those of my sons and daughters whole.” Rabbi Yitzchak replied, “How can I make your souls whole when I have only a half ma’ah coin on me?” The poor man answered, “I will complete your coin with the half ma’ah coin that I already have.” So Rabbi Yitzchak took out his coin out and gave it to him. Then Rabbi Yitzchak was shown a dream in which he was walking along the shore of the ocean and someone was trying to throw him in. He reached for the outstretched hand of Rabbi Shimon ben Yochai but just then the poor man came along and saved him. When he awoke, this is the verse that came into his mouth, “Fortunate is the one who understands [the needs of] the lowly, on a day of evil Hashem will preserve him” (Tehillim 41:2).

The principle that all negative experiences will be recognized eventually as positive developments has applied ever since in our history. This is what the Psalmist had in mind in verse 3. When he said: "Lord my G–d, when I cried out to You, and You healed me" David meant that he realized (as per Psalms 41,5: "Heal me for I have sinned against You"), that the matters which caused him to cry out were in reality only experienced in order to serve as a cure or remedy for his soul. When he went on: "Lord, You have brought me up from She-ol," our sages in Bereshit Rabbah 44,21 comment on פרשת לך לך that Abraham chose exile for his descendants in order to spare them the experience of Gehinom otherwise known as "She'ol."