"Say, therefore, 'I grant him my pact of friendship. It shall be for him and his descendants after him a pact of priesthood for all time, because he took impassioned action for his God, thus making expiation for the Israelites.'"
Pinchas is already a member of the tribe of Levi, a tribe which is known for its righteous indignation and its tendency to violence. Way back in the book of Genesis, Levi himself (along with his brother Shimon) killed off a whole town full of people because their chief's son had raped their sister Dinah. The Levites had also been the executioners after the incident of the Golden Calf. They have a tendency to go to extremes.
God curbs this tendency by channeling it. The Levites have the job of meticulously assembling and disassembling the tent of meeting and carrying it all throughout the wilderness. When the Israelites camp for a period of time, the Levites have to prepare the sacrifices. Their passion flows into an attention to detail.
Pinchas is the grandson of Aaron, the high priest. He will inherit the even more careful job of offering sacrifices, even in the area designated as the Holy of Holies. He must know that his uncles Nadav and Abihu did the same job in a way that displeased God, and died for it. His passion will also be channeled--into a tremendous devotion.
As a community and as individuals, we have within us the capacity to go to extremes in the name of what we hold most holy, whether that is the God of the Torah, Jesus, the dar al-Islam, the revolution, or the Stars and Stripes. God does not expel Pinchas for expressing this capacity but gives him his pact of friendship. We need to find ways of honoring the zealot within us--ways that make passion for the good and the right a holy force for community. May we have the strength and the wisdom to find those ways.