Комментарий к Берешит 49:7

ארור אפם כי עז CURSED BE TIIEIR WRATH, FOR IT IS POWERFUL — Even when he was reproving them he did not curse them but their anger. That is what Balaam said: (Numbers 23:8) “How can I curse them since אל hath not cursed them?” (Genesis Rabbah 99:6)

ארור אפם, they shall not succeed to take revenge in their anger and to wreak destruction when it is vented on the innocent. Seeing that they abused their brotherliness in the past, I do not wish to be associated with their method of operation. Their close association is potentially dangerous.

ארור אפם, may their level of anger be reduced, restricted. Yaakov wanted to achieve this by making it harder for them to earn their livelihood, so that they would be fully occupied doing that and caring for their families. They would have to spend their energies by traveling far and wide to secure their livelihood. However, the status of priesthood would remain the domain of the firstborn as it had been before Reuven became guilty of his indiscretion. This status was changed only after the sin of the golden calf when it was transferred en masse to the Levites (some of them). Compare Deuteronomy 10 8, בעת ההיא וגו'.