Malachi 2:4 - Albert Barnes' Notes on the Bible

And ye shall know that I have sent this commandment unto you: - this, which He had just uttered. They who believe not God when threatening, know that He is in earnest and not to be trifled with, through His punishing. “That My covenant might be with Levi.” God willed to punish those who at that time rebelled against Him, that He might spare those who should come after them. He chastened the fathers, who showed their contempt toward Him, that their sons, taking warning thereby, might not be cut off. He continues to say, what the covenant was, which He willed still to be, if they would repent.