John Gill Bible Commentary

And that was counted unto him for righteousness,.... Not for his justifying righteousness before God; for all the works of righteousness done by the best of men cannot justify them before him, much less a single action: but his executing judgment in the manner he did, or slaying the above two persons, was esteemed a righteous action by the Lord himself; who upon it caused the plague to cease, and likewise gave to Phinehas the covenant of an everlasting priesthood, and to his posterity; whereby the action had eternal honour put upon it, and was sufficiently secured from the calumny of men; who might condemn it as a rash action done by a private person, assuming the office of a public magistrate; and as being a cruel one, not giving the criminals time for repentance. But all this is set aside by the testimony of God himself, approving of it; and so it continues to be esteemed, as it is said it should, unto all generations for evermore: whenever it is spoken of, it is spoken of with commendation, as a righteous action, as expressive of true zeal for the Lord of hosts. Moreover, the covenant made with him upon it, which confirmed the justness of it, that taking place in Zadok, a priest of his line, continued in it till the Messiah came, who is a Priest for ever: see Eze 44:15.