Musar do Wyjścia 34:6

Those who subdue their souls' anger and prevail upon their nature to restrain it, have been described as noble and characterized as exalted. Thus the sage said (Prov. xvi. 32), "He that is slow to anger is better than the mighty." This is one of the thirteen attributes ascribed to God, exalted is He, in the passage (Ex. xxxiv. 6), "And the Lord passed by before him," etc. It is said that as scab is a disease of the body, so is wrath a disease of the soul. The moral man must not become wrathful often, because, by reason of his wrath, he is compelled to bear burdens. Thus saith the sage (Prov. xix. 19), "A man of great wrath shall bear punishment."

Mercy is a most praiseworthy quality and is one of the thirteen attributes associated with the Holy One, Blessed be He, as it is written: "Merciful and Gracious" (Exod. 34:6). A man should do as much as he can to conduct himself in this quality. And just as a person desires people to have mercy upon him in the hour of his need, so it is proper for him that he should have mercy upon anyone who is in need, as Scripture says: "And you shall love your neighbor as yourself" (Lev. 19:18).

And, in truth, how great is this mitzvah in the eyes of the Blessed L-rd, it being written (Michah 6:8): "He has told you, O man, what is good, and what the L-rd requires of you — but to do justice and to love chesed, etc." And Chazal have said (Succah 49b): "'to do justice' — this is din; 'and to love chesed' — this is gemiluth chasadim." And he also fulfills in this the mitzvah of (Devarim 29:9): "And you shall walk in His ways," as we find in Sifrei on the verse (Ibid. 10:12): "'to walk in all His ways' — these are the ways of the Holy One Blessed be He, as it is written (Shemoth 34:6): 'Hashem, Hashem, the G-d who is merciful and gracious, slow to anger, and abundant in chesed, etc.'" And Chazal say (Bava Metzia 30b): "R. Yosef taught (Shemoth 18:20): 'And you shall apprise them of the way' — this is gemiluth chasadim."