Numbers 25:12 - Albert Barnes' Notes on the Bible

My covenant of peace - Equivalent to “the covenant of My peace.” God established with Phinehas in particular that covenant which He had made generally with all his people; and among its blessings peace is especially mentioned, because of the peace between God and the congregation which Phinehas had brought about. As an additional gift there is assigned to him and his seed forever the office of peace-making, the legitimate function of the priesthood (compare Ephesians 2:14); and the covenant was thus to him a covenant not only of peace but of life (compare the marginal reference). Phinehas became highpriest after the death of his father Eleazar, and the office, with a short interruption from the days of Eli to those of David, when for unknown reasons it was filled by the descendants of his uncle Ithamar, was perpetuated in his line; nor indeed is it known to have departed from that line again until the typical priesthood of the sons of Aaron was merged in the actual priesthood of the Saviour of mankind.