Jamieson, Fausset and Brown on Malachi 1:7

7. ye offer, &c.--God's answer to their challenge (Mal 1:6), "Wherein have we despised?"

polluted bread--namely, blemished sacrifices (Mal 1:8, 13, 14; De 15:21). So "the bread of thy God" is used for "sacrifices to God" (Le 21:8).

polluted thee--that is, offered to thee "polluted bread."

table of the Lord--that is, the altar (Eze 41:22) (not the table of showbread). Just as the sacrificial flesh is called "bread."

contemptible--(Mal 1:12, 13). Ye sanction the niggardly and blemished offerings of the people on the altar, to gain favor with them. Darius, and probably his successors, had liberally supplied them with victims for sacrifice, yet they presented none but the worst. A cheap religion, costing little, is rejected by God, and so is worth nothing. It costs more than it is worth, for it is worth nothing, and so proves really dear. God despises not the widow's mite, but he does despise the miser's mite [Moore].