Albert Barnes Commentary Malachi 1:12

"But ye profane it, in that ye say, The table of Jehovah is polluted, and the fruit thereof, even its food, is contemptible." — Malachi 1:12 (ASV)

And you have profaned it (you are habitually profaning it), in that you say, "It was the daily result of their daily lives and acts."

It is probable that the priests did not use such words, but by their very deeds, they proclaimed this aloud, as in the passage: The fool has said in his heart, There is no God.

For when someone is seen to be a despiser, even if they do not say it in words, yet by their very deeds and by the crookedness of their lives, they almost cry out, "There is no God."

For those who live as though God does not behold them, and do all things recklessly and unholily, deny God by their own deeds and works.

So, those who are not earnest in preserving for the holy altar the reverence due to it, by the very things they do, say:

The table of the Lord is despised—not the "table of showbread," since it is so called in reference to the sacrifice offered on it. Ezekiel had probably so called the altar, which he saw in his vision of the new temple (Ezekiel 44:16). It is what was previously called "the altar": an altar, concerning the sacrifices offered to God; and a "table," concerning the food of the sacrifice received from it. Both names, "altar" (Matthew 5:23; Hebrews 13:10) and "table" (1 Corinthians 10:21), being accepted in the New Testament, were also received in the early Church. For each represented one side of the great eucharistic action, as it is a Sacrifice and a sacrament. But the title "altar" was the earliest.

It may be here a different type of profanity from the priests. They connived at the sin of the people in sacrificing the maimed animals which they brought. And yet, since they received their food from these sacrifices, and such animals were likely to have been neglected and ill-conditioned, they may very probably have complained about the poverty of their situation and despised the whole service. For the words used, "its produce, the eating of it is contemptible," belong to their portion, not to what was consumed by fire. With this agrees their cry.