O my soul, come not into their secret; unto their assembly, my spirit, be not united: for in their anger they slew a man, and in their self-will they dug down a wall.
Read Chapter 49
Ambrose of Milan
Likewise, when he said to Simeon and Levi, “I will divide you in Jacob and scatter you in Israel,” he revealed that they were to be redeemed in the gathering together of the nations. For when the shepherd has been struck down, the flock that was previously brought together is scattered; thus one who did not belong could enter in and all Israel could be saved. And we ought in particular to assume this as regards the tribe of Levi, for it appears that the Lord Jesus traced his origin from that tribe, as concerns his taking on of the body. Of that tribe are the priests Levi and Nathan, and, in the Gospel which he wrote, St. Luke counted them among the ancestors of the Lord. For the Priest of the Father and Chief of all priests, even as it is written, “You are a priest forever,” should have laid claim to succession from a priestly line. On this account also Moses blessed this tribe and said, “Give to Levi the lot of his own approbation, and to the holy man his truth.”
Slew a man, viz., Sichem, the son of Hemor, with all his people, chap. xxxiv. Mystically and prophetically it alludes to Christ; whom their posterity, viz., the priests and the scribes, put to death. (Challoner)
A wall, Sichem, which they destroyed: or, according to the Septuagint, "they ham-strung "a bull, as the same Hebrew word signifies; both which may refer to the prince of the town, or to Joseph, (Calmet) in whose persecution these two were principally concerned. Jacob declares, he had no share in their attack upon the people of Sichem: his soul, or his glory, was not impaired by their misconduct. (Haydock)
Read the gospel and you will find it written down; the scribes were from the tribe of Simeon, and the high priests from that of Levi. Since the decision to arrest the Christ and to execute him was taken in their council, the prophet foreknowing that said, “O my soul, come not into their council!” In this passage he talks about the council where they took their decisions by searching for a reason through which they might accuse Christ, so that “they took counsel together in order to arrest Jesus by stealth and kill him.” And Isaiah says the same: “Woe to their soul, for they have devised an evil counsel against themselves, saying, ‘Let us bind the just one, for he is burdensome to us.’ ”
Then, in a reference to their crimes Jacob applies a curse in the words “Cursed be their rage for its ferocity and their frenzy for its willfulness”: this touches on the stratagem they employed in deceiving the inhabitants of Shechem and imposed on them by guile. Their rage was “ferocious,” he says, headstrong, irrational. “Their frenzy is cursed for its willfulness.” When the Shechemites came to believe they had won great favor with them, then it was that Simeon and Levi vented their baleful frenzy and deployed the tactics of a foe against them. Referring to their exploit as sins, he foretells as well the punishment for it that awaits them: “I will disperse them in Jacob and scatter them in Israel.” They will be scattered in all directions so that this very thing will be obvious to everyone, namely, that they had persisted in committing this crime out of bravado.
God forbid, Jacob is saying, that I should share their evil intent or associate myself with their unjust doings. “Because in the heat of their passion they slew people”; their rage turned irrational …. After all, even if Shechem had sinned, there was no need to turn their thirst for blood against everyone. “And in their fury they cut down a bull”; there is reference here to the son of Hamor, calling him a bull because of his hotblooded maturity.
As for the historical account, it seems that in this passage [Simeon and Levi] are reproached because, through deceit and fraud, they slaughtered Shechem, the son of Hamor, who after sleeping with their sister had tried to associate himself with the family of Israel. They also destroyed the whole people [of Shechem], so that Israel himself, their father, said to them, “You made me odious in this world.” Therefore he curses their cruelty and their recklessness and declares he will scatter them amid the people of Israel, and that from them the Levites and the priests who do not have their own inheritance of land will descend.