Psalms 78:31

“And that was counted unto him for righteousness, etc.] 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…”

“The wrath of God came upon them - See Numbers 11:33. And slew the fattest of them - literally, “slew among their fat ones.” That is, The most vigorous among them were cut down; the people most eminent for rank, for influence, for strength, for valor. How far this was the natural effect of indulgence in eating, and how far it was a direct miracle, cannot now be ascertained. In either case it would equally show the divine displeasure. And smote down - Margin, as in Hebrew, “made to bow.” That is, they were made to bow in death. The chosen men of Israel - Margin, “Young men.” The idea is that of select men; men that would be chosen from among the others; men distinguished for vigor or…”

“Mightiest - The most healthy and strong, who probably were most desirous of this food, and fed most eagerly upon it. Psalms 78:33”

“smote down: Heb. made to bow chosen men: or, young men, Psa 78:63 Psalms 78:32”