לְמַֽעַן־שִׁמְךָ֥ יְהוָ֑ה וְֽסָלַחְתָּ֥ לַ֝עֲוֺנִ֗י כִּ֣י רַב־הֽוּא׃
En faveur de ton nom, Seigneur, pardonne mon iniquité, si grande qu’elle puisse être.
Or HaChaim
במתי מעט, "few in numbers." This is a reference to the relatively weak forces of Satan at that time. Afterwards these forces increased manifold due to the active co-operation of man himself. This is why the Torah continues: ויהי שם לגוי גדול ועצום "and while there it became a powerful nation." This is the mystical dimension of Psalms 25,11: וסלחת לעוני כי רב הוא "and pardon my iniquity though it is great." Rabbi Yitzchak Luria explained that the word רב, "great," refers to the evil urge whose powers are great. The fact that G'd commanded us to perform the rites of the scape-goat on the Day of Atonement is proof that Satan's power must not be discounted. G'd commanded that we present one scape-goat each to Him and to the Azzazel (Leviticus 16,8).
Chizkuni
אם נא מצאתי חן בעיניך ה' ילך נא ה׳ בקרבנו, “if I have indeed found favour in Your eyes o G-d, may the Lord walk among us, please.” The attribute Moses addresses in this verse is both times the attribute of His name spelled Adonai.” כי עם קשי עורף הוא, “although it is a stiffnecked people.” Moses concurred with G-d Who had described this people as “stiffnecked” in Exodus 33,3. G-d had used it as an excuse for not walking amongst that people. Moses uses this very fact as justifying his request that G-d remain present among them. What better restraining influence against the evil urge is there than the very presence of G-d, the Creator, being in its midst?An alternate explanation of this argument: “Even though they are a stiffnecked people.” We find the same logic in Psalms 25,11: וסלחת לעוני כי רב הוא, “forgive my sin even though it be great.” Why do I plead that You walk amongst us? Because the angel has no authority to forgive any trespasses against You, as You, Yourself have pointed out. It is therefore better that seeing that they are a stiff necked people, You should be there to forgive one sin of the people at a time, instead of letting them accumulate sins which, collectively, will prove too difficult to forgive.
Chizkuni
כי לא ישא לפשעכם כי שמי בקרבו, “for he has no authority to forgive your deliberate sins, as My Name is within him.” G-d means that even though he (that angel) is a celestial creature, and therefore Divine, He cannot “forgive” any trespass against Him. Another place in the Bible where we encounter a similar thought is Psalms 25,11, למען שמך וסלחת לעוני כי רב הוא, “as befits Your name, o Lord, pardon my iniquity.” Other examples of “irregularities” in treatment, are Genesis 48,14, where Yaakov insisted in giving preferential treatment to Ephrayim although Menashe was the firstborn. Another example is found in Psalms 74,20-21: הבט לברית כי מלאו מחשכי ארץ נאום חמס וגו', “Look to the covenant, for the dark places of the land are full of the haunts of lawlessness. Let not the downtrodden turn away disappointed, let the poor and needy praise Your name.” [Here the people ask to be promoted instead of being demoted. Ed.]