Musar su Salmi 32:5

And King Solomon, peace be upon him, spoke about the matter of repentance and specified this topic. And he surely opened his words and said (Proverbs 28:12), "When the righteous exult there is great glory, but when the wicked rise up, men will be sought." The explanation [of this] is that the righteous will exalt and honor people about all the good traits that are found with them; but the wicked seek peoples' blemishes and their mistakes, to put them down - even when they have already left these actions and returned in repentance. Afterwards he said (Proverbs 28:13), "He who covers up his faults will not succeed; but he who confesses and gives them up will find mercy." For even though a penitent should not reveal his iniquities to people - as is to be understood from that which is stated, "but when the wicked rise up, men will be sought" - he is obligated to confess them [privately], like the matter that is stated (Psalms 32:5), "Then I acknowledged my sin to You; I did not cover up my guilt." And it is [also] stated (Jeremiah 2:35), "Lo, I will bring you to judgment for saying, 'I have not sinned.'" But the Sages of Israel, may their memory blessed, explained (Yoma 86b) [that] there are times when he who covers up his faults will not succeed - like with sins between a man and his fellow. As he does not attain atonement until he returns what was stolen, extorted or taken unjustly; and until he asks to be pardoned for that which he annoyed him, embarrassed him or spoke evil speech about him. [Likewise must he not cover up his] sins between a man and the Omnipresent that have become known to people. For one who sins publicly desecrates [God's] name (but Rashi, may his memory be blessed, in the Chapter [entitled] Yom HaKippurim, understands it in a different way. See there.) So he is obligated to grieve and mourn about it in front of people to sanctify [God's] name. And this is [the meaning of] that which is written (Jeremiah 31:19), "Now that I have turned back, I am filled with remorse; now that I am made aware, I strike my thigh." The meaning of, "I am filled with remorse," is regret and pain. For the essence of repentance is bitterness of the heart, as we have explained. And [the meaning of,] "now that I am made aware, I strike my thigh," is after people have been made aware and my iniquities have been publicized, I mourned with actions that were visible to people. [This is] like (Ezekiel 21:17), "strike the thigh"; and it is [also] stated (Job 33:27), "He declares to men, 'I have sinned; I have perverted what was right.'"

9. A fast day is an appropriate time to lay out one’s sins before the Holy One Blessed is He. Then the Satan will be unable to detract from one’s sacrifice or prayer with his indictments. Thus the Zohar relates in Parashas Vayikra (20a): Rabbi Chiya and Rabbi Yose were traveling along a road. While they were walking Rabbi Yose said to Rabbi Chiya, “Come let us engage in Torah study.” Rabbi Chiya began, “[It is written,] ‘I will tell You my sin’ (Tehillim 32:5). From here we learn that any man who conceals his sins and does not acknowledge them before the holy King and seek mercy over them is not granted to open the portal of repentance. But if a person does acknowledge them, then the Holy One Blessed is He has mercy upon him and the attribute of mercy overwhelms the attribute of judgment. “This is especially true if he weeps, for all the other gates of Heaven are blocked up, but the gate of tears is open and his prayers will be accepted. Therefore whoever acknowledges his sins honors the King and causes mercy to overwhelm judgment. Concerning this was it written, ‘He who offers confession honors Me’ (Tehillim 50:23). [And why is the word ‘honor’ written with two nuns (yechabdaneni)?] Because there are two aspects to [Hashem’s] honor, one On High and one below, one in this world and one in the next.”