Wherefore say, Behold, I give unto him my covenant of peace:

Wesley's Notes

25:12 My covenant of peace - That is, the covenant of an everlasting priesthood, as it is expounded, Nu 25:13, which is called a covenant of peace, partly with respect to the happy effect of this heroical action of his, whereby he made peace between God and his people; and partly with regard to the principal end of the priestly office, which was constantly to do that which Phinehas now did, even to meditate between God and men, to obtain and preserve his own and Israel's peace and reconciliation with God, by offering up sacrifices and incense, and prayers, to God on their behalf, as also by turning them away from iniquity, which is the only peace - breaker, and by teaching and pressing the observation of that law, which is the only bond of their peace.

Matthew Henry's Concise Commentary

25:6-15 Phinehas, in the courage of zeal and faith, executed vengeance on Zimri and Cozbi. This act can never be an example for private revenge, or religious persecution, or for irregular public vengeance.