Charles Ellicott Commentary Genesis 49:7

"Cursed be their anger, for it was fierce; And their wrath, for it was cruel: I will divide them in Jacob, And scatter them in Israel." — Genesis 49:7 (ASV)

Cursed ... — Jacob condemns Simeon and Levi not because they were angry, but because they vented their anger in a treacherous and violent manner. The next sentence literally is, And their rage, for it was hard. The indignation at Joseph’s dreams, which he innocently told them, led them to a harsh and inhuman act .

I will divide them ... — This prediction was equally fulfilled in the fact that neither the tribe of Simeon nor the tribe of Levi possessed any political importance in Israel. The brothers had banded together to oppress their kin; their descendants were powerless. But in every other respect, the fulfilment was utterly diverse. In the wilderness, the Simeonites dwindled from 59,300 to 22,200 men (Numbers 1:23; Numbers 26:14); and after the conquest of Canaan, they were so feeble that they were assigned only fifteen towns, scattered about in the territory of Judah.

And there they melted away, being either absorbed into the tribe among whom they lived, or withdrawing to wander as nomads in the wilderness of Paran. In Levi’s case, the curse was changed into a blessing by the faithfulness of the tribe on a very trying occasion (Exodus 32:26–28); and we learn from it the great lesson that the Divine rewards and punishments, even when specified in prophecy, are nevertheless conditional on human conduct. Of this diversity of fulfilment, there is not the slightest indication in Jacob’s blessing, while in that of Moses, the lot of Levi is described in terms of the highest praise, and that of Simeon is passed over in inglorious silence.