ויעבור ה' על פניו ויקרא
א"ר יוחנן אלמלא מקרא כתוב אי אפשר לאומרו מלמד שנתעטף הקב"ה כשליח צבור והראה לו למשה סדר תפלה אמר לו כל זמן שישראל חוטאין יעשו לפני כסדר הזה ואני מוחל להם
ה' ה' אני הוא קודם שיחטא האדם ואני הוא לאחר שיחטא האדם ויעשה תשובה אל רחום וחנון
אמר רב יהודה ברית כרותה לי"ג מדות שאינן חוזרות ריקם שנאמר (שמות לד, י) הנה אנכי כורת ברית
...The verse states: “And the Lord passed by before him, and proclaimed...” (Exodus 34:6).
Rabbi Yoḥanan said: Were it not explicitly written in the verse, it would be impossible to say this, as it would be insulting to God’s honor:
The verse teaches that the Holy One, Blessed be He, wrapped Himself in a prayer shawl like a prayer leader and showed Moses the structure of the order of the prayer. He said to him: Whenever the Jewish people sin, let them act before Me in accordance with this order. Let the prayer leader wrap himself in a prayer shawl and publicly recite the thirteen attributes of mercy, and I will forgive them.
The verse continues: “The Lord, the Lord,” and it should be understood as follows: I am He before a person sins, and I am He after a person sins and performs repentance, as God does not recall for him his first sins, since He is always “God, merciful and gracious” (Exodus 34:6).
Rav Yehuda said: A covenant was made with the thirteen attributes that they will not return empty-handed, meaning that if one mentions them, one will certainly be answered, as it is stated in this regard: “Behold, I make a covenant” (Exodus 34:10).
The extraction of God’s thirteen merciful attributes from Exodus 34: 6-7 is not obvious! As may be imagined, there are numerous commentaries that attempt to connect thirteen attributes to the wording in these two biblical verses. Note that in Midrash Tehillim,[1], the Sages count ten while Rav counts eleven, and that in the Dead Sea Scroll of Thanksgiving (16:16), the count is also ten.[2] The following enumeration of thirteen attributes is based on the list in the Conservative Movement’s Mahzor Lev Shalem:[3]
1 - Adonai: I am God before you sin.
2- Adonai: I am God after you sin.
3- El (God): Merciful to all, Gentile and Jew.
4- Rahum (Compassionate): To those with merit.
5- Vehanun (Gracious): To those without merit.
6- Erekh apayim (Patient): With the wicked, who may repent.
7- Verav hesed (Abounding in kindness): With those in need in kindness.
8- Ve’emet (And Faithfulness): Rewarding those who do My will.
9- Notzer hesed la’alafim (Assuring love for a thousand generations): When you do good deeds.
10- Nosei avon (Forgiving iniquity): When you sin deliberately.
11- Vafesha (And transgression): When you rebel maliciously.
12- Vehata’ah (And sin): When you sin unintentionally.
13- Venakeih (And “clearing,” i.e., granting pardon): When you repent.
[1] Solomon Buber edition, Vilna, 1891, p. 416.
[2] Midrash Tehillim and the Dead Sea Scroll of Thanksgiving are cited in Hayyim Herman Kieval, The High Holy Days: A Commentary on the Prayerbook of Rosh Hashanah and Yom Kippur, Yom Kippur section of the book, 416, n. 19.
[3] Edited by Edward Feld, 2010, p. 336. The following sources are cited there:
-Rabbeinu Tam, France, (1100-1171 France, in Tosafot, Rosh HaShanah, 17b, s.v. Shelosh Esreih Middot).
-Sefer Abudraham HaShalem (14th century Spain, 1963 edition), pp. 251-252.
-Sefer HaBakashah by Moshe HaKohen Niral, (1788 Metz, France).