Rabbeinu Yonah opens by establishing that teshuvah is an expression of God's boundless mercy, and enumerates twenty principles of teshuvah including remorse, abandonment of sin, verbal confession, prayer, and humility. He emphasizes that God eagerly awaits the sinner's return.
הַשַּׁעַר הָרִאשׁוֹן – בְּבֵאוּר הַתְּשׁוּבָה וְעִקָּרֶיהָ. מִן הַטּוֹבוֹת אֲשֶׁר הֵיטִיב הַשֵּׁם יִתְבָּרַךְ עִם בְּרוּאָיו, כִּי הֵכִין לָהֶם הַדֶּרֶךְ לַעֲלוֹת מִתּוֹךְ פַּחַת מַעֲשֵׂיהֶם וְלָנוּס מִפַּח פִּשְׁעֵיהֶם, לַחְשֹׂךְ נַפְשָׁם מִנִּי שַׁחַת וּלְהָשִׁיב מֵעֲלֵיהֶם אַפּוֹ, וְלִמְּדָם וְהִזְהִירָם לָשׁוּב אֵלָיו כִּי יֶחֶטְאוּ לוֹ, לְרֹב טוּבוֹ וְיָשְׁרוֹ כִּי הוּא יָדַע יִצְרָם, שֶׁנֶּאֱמַר (תהלים כה, ח): "טוֹב וְיָשָׁר ה' עַל כֵּן יוֹרֶה חַטָּאִים בַּדָּרֶךְ", וְאִם הִרְבּוּ לִפְשֹׁעַ וְלִמְרוֹד וּבֶגֶד בּוֹגְדִים בָּגָדוּ, לֹא סָגַר בַּעֲדָם דַּלְתֵי תְּשׁוּבָה, שֶׁנֶּאֱמַר (ישעיה לא, ו): "שׁוּבוּ לַאֲשֶׁר הֶעְמִיקוּ סָרָה". וְנֶאֱמַר (ירמיה ג, כב): "שׁוּבוּ בָּנִים שׁוֹבָבִים אֶרְפָּה מְשׁוּבֹתֵיכֶם". וְהֻזְהַרְנוּ עַל הַתְּשׁוּבָה בְּכַמָּה מְקוֹמוֹת בַּתּוֹרָה, וְהִתְבָּאֵר, כִּי הַתְּשׁוּבָה מְקֻבֶּלֶת גַּם כִּי יָשׁוּב הַחוֹטֵא מֵרֹב צָרוֹתָיו, כָּל שֶׁכֵּן אִם יָשׁוּב מִיִּרְאַת הַשֵּׁם וְאַהֲבָתוֹ, שֶׁנֶּאֱמַר (דברים ד, ל): "בַּצַּר לְךָ וּמְצָאוּךָ כֹּל הַדְּבָרִים הָאֵלֶּה בְּאַחֲרִית הַיָּמִים וְשַׁבְתָּ עַד ה' אֱלֹהֶיךָ וְשָׁמַעְתָּ בְּקוֹלוֹ". וְהִתְבָּאֵר בַּתּוֹרָה, כִּי יַעֲזֹר ה' לַשָּׁבִים כַּאֲשֶׁר אֵין יַד טִבְעָם מַשֶּׂגֶת וִיחַדֵּשׁ בְּקִרְבָּם רוּחַ טְהוֹרָה לְהַשִּׂיג מַעֲלַת אַהֲבָתוֹ, שֶׁנֶּאֱמַר (דברים ל, ב): "וְשַׁבְתָּ עַד ה' אֱלֹהֶיךָ וְשָׁמַעְתָּ בְקֹלוֹ כְּכֹל אֲשֶׁר אָנֹכִי מְצַוְּךָ הַיּוֹם אַתָּה וּבָנֶיךָ בְּכָל לְבָבְךָ וּבְכָל נַפְשֶׁךָ". וְאוֹמֵר בְּסוֹף הָעִנְיָן (דברים ל, ו): "וּמָל ה' אֱלֹהֶיךָ אֶת לְבָבְךָ וְאֶת לְבַב זַרְעֶךָ" – לְהַשִּׂיג אַהֲבָתוֹ. וְהַנְּבִיאִים וְהַכְּתוּבִים דִּבְּרוּ תָּמִיד עַל דְּבַר הַתְּשׁוּבָה, עַד כִּי בָּאוּ עִקְּרֵי הַתְּשׁוּבָה כֻּלָּם מְפֹרָשִׁים בְּדִבְרֵיהֶם כַּאֲשֶׁר יִתְבָּאֵר. וְהִנֵּה מַדְרֵגוֹת רַבּוֹת לַתְּשׁוּבָה, וּלְפִי הַמַּדְרֵגוֹת יִתְקָרֵב הָאָדָם אֶל הַקָּדוֹשׁ בָּרוּךְ הוּא. וְאָמְנָם לְכָל תְּשׁוּבָה תִּמָּצֵא סְלִיחָה, אַךְ לֹא תִּטְהַר הַנֶּפֶשׁ טֹהַר שָׁלֵם לִהְיוֹת הָעֲוֹנוֹת כְּלֹא הָיוּ, זוּלָתִי כַּאֲשֶׁר יְטַהֵר הָאָדָם אֶת לִבּוֹ וְיָכִין אֶת רוּחוֹ כַּאֲשֶׁר יִתְבָּאֵר. וְכֵן כָּתוּב (תהלים לב, ב): "אַשְׁרֵי אָדָם לֹא יַחְשֹׁב ה' לוֹ עָוֹן וְאֵין בְּרוּחוֹ רְמִיָּה", וּכְעִנְיָן הַבֶּגֶד הַצָּרִיךְ כִּבּוּס, כִּי הַמְּעַט מִן הַכִּבּוּס יוֹעִיל בּוֹ לְהַעֲבִיר הַגֹּעַל מִמֶּנּוּ, אַךְ לְפִי רֹב הַכִּבּוּס יִתְלַבֵּן. וְכֵן כָּתוּב (תהלים נא, ד): "הֶרֶב כַּבְּסֵנִי מֵעֲוֹנִי", וּתְכֻבַּס הַנֶּפֶשׁ מִן הֶעָוֹן כְּפִי אֲשֶׁר תְּכַבֵּס אֶת לִבָּהּ, שֶׁנֶּאֱמַר (ירמיה ד, יד): "כַּבְּסִי מֵרָעָה לִבֵּךְ יְרוּשָׁלִַם". וְאָמְרוּ רַבּוֹתֵינוּ זִכְרוֹנָם לִבְרָכָה (ע"ז יט, א) "אַשְׁרֵי אִישׁ יָרֵא אֶת ה'" (תהלים קיב, א) – בְּעוֹדוֹ אִישׁ, רְצוֹנָם לוֹמַר, כִּי תְּשׁוּבַת הָאָדָם הַמְּעֻלָּה בִּימֵי בְּחוּרוֹתָיו בְּעוֹד כֹּחוֹ עָלָיו וְיִתְגַּבֵּר עַל יִצְרוֹ. אָכֵן כָּל תְּשׁוּבָה מוֹעִילָה, כְּמוֹ שֶׁנֶּאֱמַר (תהלים צ, ג): "תָּשֵׁב אֱנוֹשׁ עַד דַּכָּא וַתֹּאמֶר שׁוּבוּ בְנֵי אָדָם", וְאָמְרוּ רַבּוֹתֵינוּ זִכְרוֹנָם לִבְרָכָה (ירושלמי חגיגה ב, א) עַד דִּכְדּוּכָהּ שֶׁל נֶפֶשׁ. עַתָּה נְבָאֵר עִקְּרֵי הַתְּשׁוּבָה.
In explanation of repentance and its principles Among the good things which God, may He be blessed, has bestowed upon His creations is the path which He prepared for them to ascend from the baseness of their actions, to escape the trap of their inequities, to hold their souls back from destruction and to remove His anger from upon them. Because of His goodness and uprightness, He has taught them and warned them to return to Him when they sin against Him - for He understands their nature, as it is stated (Psalms 25:8), "Good and upright is the Lord; therefore He shows sinners the way." [Even] if they greatly sin and rebel and act like treacherous betrayers - He does not close the doors of repentance to them, as it is stated (Isaiah 31:6), "Return, to Him to whom they have been so shamefully false." It is [also] stated (Jeremiah 3:22), "Turn back, O rebellious children, I will heal your afflictions." We are warned about repentance in several places in the Torah. It is explained that repentance is accepted even when the sinner repents because of his many troubles - how much more so [will it be accepted] if he returns because of fear or love of God - as it is stated (Deuteronomy 4:30), "When you are in distress because all these things have befallen you and, in the end, return to the Lord your God and obey Him." It is explained in the Torah that God will help those who repent beyond what their natural ability would allow; and that He renews a pure spirit within them, to reach great heights in His love - as it is stated (Deuteronomy 30:2), "And you return to the Lord your God, and you and your children heed His command with all your heart and soul, just as I enjoin upon you this day." Further, it is stated about the body of the matter (Deuteronomy 30:6), "Then the Lord, your God, will circumcise your heart and the hearts of your offspring," to acquire love for Him. And the Prophets and Writings constantly speak on the subject of repentance, such that the principles of repentance are all explained in their words, as will be explained. And behold that there are many levels of repentance. It is true that you will find forgiveness for any repentance. However the soul will only find complete purification - to be as if the iniquities never had been - when a person purifies his heart and prepares his spirit, as will be explained. And so is it written (Psalms 32:2), "Happy is the man whom the Lord does not hold guilty, and in whose spirit there is no deceit." And it is like the matter of a garment that needs washing: For a little washing will be effective to remove its soiling. However, it will [only] whiten according to the amount of washing. And so is it written there (Psalms 51:4), "Wash me thoroughly of my iniquity." And the soul will be washed from iniquity according to how you wash its heart, as it is stated (Jeremiah 4:14), "Wash your heart clean of wickedness, O Jerusalem." And our Rabbis, may their memory be blessed, said (Avodah Zarah 19a), "'Happy is the man who fears the Lord' (Psalms 112:1) - when he is still a man." This means to say that the most elevated repentance of a man is in the days of his youth - [when] he overcomes his impulse when his strength is still with him. However any repentance is effective, as it is stated (Psalms 90:3), "You return man to dust; You said, 'Return you mortals!'" And our Rabbis, may their memory be blessed, said (Yerushalmi Chagigah 2:1), "Until the soul turns to dust."