(Devarim 33:8) "And of Levi he said": Why was this (blessing) said of him (and not of Shimon)? Shimon and Levi drank of one cup, viz. (Bereshith 49:7) "Cursed be their wrath, for it is fierce, and their anger, for it is sore. I shall divide them in Jacob, and I shall scatter them in Israel." This is analogous to (the situation of) two, who borrowed from the king.
One paid him back, and borrowed from him again, and the other — not only did he not pay him back, but he borrowed again. Thus, Shimon and Levi: Both "borrowed" in Shechem, viz. (Bereshith 34:25) "And there took, two sons of Jacob, Shimon and Levi, each man his sword, and came upon the city (Shechem) secure, (in that the men were ailing from the circumcision), and they killed every male." Levi paid back what he borrowed in the desert, (in the incident of the golden calf) viz. (Shemoth 32:26) "And Moses stood in the gate of the camp, and he said 'Whoever is for the L-rd, (let him come) to me!'
And there gathered unto him all the sons of Levi, etc." And he returned and "borrowed" from the L-rd in Shittim, viz. (Bamidbar 25:11) "Pinchas the son of Elazar the son of Aaron the Cohein turned My wrath away from the children of Israel when he raged My rage in their midst, and I did not consume the children of Israel in My wrath" — whereas Shimon, not only did he not repay the loan, but he went and "borrowed" again, viz. (Ibid. 14) "And the name of the man of Israel who was smitten, who was smitten together with the Midianite woman, was Zimri the son of Salu, chief of a father's house in the house of Shimon."