Pinchas was rewarded with peace; Hashem would be amicable towards him as a symbol of His gratitude. Ibn Ezra interprets this peace as a protection from retaliation at the hands of Zimri’s henchmen and friends. Regardless of the type of peace, we may question the form of middah k’neged middah, measure for measure, of this reward. The reward is to be commensurate with the mitzvah. Pinchas performed an act of zealousness; should his reward be a covenant of peace?
Horav M.D. Solveitzchik, Shlita, cites his grandfather, Rav Chaim Brisker, zl, who commented that Pinchas’s act of kana’us was in reality an act of peace, since it was performed l’shem Shomayim, for the sake of Heaven. His intentions were so noble, his virtue so pure, that he transformed what might have been perceived as an act of violence into an act of reconciliation.
Rav Chaim made an analogy in order to demonstrate the difference between the genuine kana’i and the one who merely portrays himself as a kana’i. The situation can be compared to a case in which one purchases a cat to rid his home of a profusion of mice. Undoubtedly, the owner of the house and the cat both dislike mice and want them destroyed. There is a difference, however, between the home-owner and the cat: The owner would rather no mouse disturb his home at all, while the cat is pleased to encounter and kill as many mice as he can.
The same idea may be applied to the kana’i. He who puts on a show of zealousness is nothing more than a charlatan who always seem to get involved when there is a scandal or conflict in a community. Indeed, such an individual, like the “cat,” looks for situations in which he can demonstrate his zealousness. The real kana’i, on the other hand, would be quite satisfied if he had no battles to fight.