(יח) מִי־אֵ֣ל כָּמ֗וֹךָ נֹשֵׂ֤א עָוֺן֙ וְעֹבֵ֣ר עַל־פֶּ֔שַׁע לִשְׁאֵרִ֖ית נַחֲלָת֑וֹ לֹא־הֶחֱזִ֤יק לָעַד֙ אַפּ֔וֹ כִּֽי־חָפֵ֥ץ חֶ֖סֶד הֽוּא׃ (יט) יָשׁ֣וּב יְרַֽחֲמֵ֔נוּ יִכְבֹּ֖שׁ עֲוֺֽנֹתֵ֑ינוּ וְתַשְׁלִ֛יךְ בִּמְצֻל֥וֹת יָ֖ם כָּל־חַטֹּאותָֽם׃ (כ) תִּתֵּ֤ן אֱמֶת֙ לְיַֽעֲקֹ֔ב חֶ֖סֶד לְאַבְרָהָ֑ם אֲשֶׁר־נִשְׁבַּ֥עְתָּ לַאֲבֹתֵ֖ינוּ מִ֥ימֵי קֶֽדֶם׃
(18) Who is a God like You, Forgiving iniquity And remitting transgression; Who has not maintained His wrath forever Against the remnant of His own people, Because He loves graciousness! (19) He will take us back in love; He will cover up our iniquities, You will hurl all our sins Into the depths of the sea. (20) You will keep faith with Jacob, Loyalty to Abraham, As You promised on oath to our fathers In days gone by.
(ה) מִֽן־הַ֭מֵּצַ֥ר קָרָ֣אתִי יָּ֑הּ עָנָ֖נִי בַמֶּרְחָ֣ב יָֽהּ׃ (ו) יְהוָ֣ה לִ֭י לֹ֣א אִירָ֑א מַה־יַּעֲשֶׂ֖ה לִ֣י אָדָֽם׃ (ז) יְהוָ֣ה לִ֭י בְּעֹזְרָ֑י וַ֝אֲנִ֗י אֶרְאֶ֥ה בְשֹׂנְאָֽי׃ (ח) ט֗וֹב לַחֲס֥וֹת בַּיהוָ֑ה מִ֝בְּטֹ֗חַ בָּאָדָֽם׃ (ט) ט֗וֹב לַחֲס֥וֹת בַּיהוָ֑ה מִ֝בְּטֹ֗חַ בִּנְדִיבִֽים׃ (י)
(5) In distress I called on the LORD; the Lord answered me and brought me relief. (6) The LORD is on my side, I have no fear; what can man do to me? (7) With the LORD on my side as my helper, I will see the downfall of my foes. (8) It is better to take refuge in the LORD than to trust in mortals; (9) it is better to take refuge in the LORD than to trust in the great.
Rabbi Jonathan Saks: Commentary to Tashlikh from pp. 936-947 of Koren-Sacks Machzor for Rosh HaShana
It is a custom, on the afternoon of the first day of Rosh HaShana (or second, if the first is Shabbat) to go to teh shore of the sea, the bank of a river, or other running stream of water, as a symbolic enactment of the words of the prophet Micah: "He God] will cast (tashlikh) into the depths of the sea all their sins" (Micah 7:19)...The first mention of the custom is in Sefer Maharil of Rabbi Jacob Moellin (d. 1425)...Many folk customs have become associated with Tashlikh, among them the custom of throwing crumbs into water as a symbolic gesture to accompany the process of repentance, begun on Rosh HaShana, as if we were "casting away" our sins. This practice was dismissed by some halakhic authorities and ridiculed by gentiles. However it is less ridiculous than it seems. Maimonides writers about the scapegoat on Yom Kippur over which the High priest confessed the sins of the people and which was then sent out into the wilderness:
"There is no doubt that sins cannot be carried like a burden, and taken off the shoulder of one being and laid on that of another. But these ceremonies are of a symbolic character, and serve to impress people with a certain idea, and to induce them to repent, as if to say: we have freed ourselves of our previous deeds, have cast them behind our backs and removed them frum us as far as possible (Guide III:46)."