What does Malachi 2:3 mean?

This verse continues God's warning to the priests about their insulting and lazy approach to worship. This particular warning involves the concept of legacy. If the priests continue to offer improper sacrifices (Malachi 1:7–8) and to degrade God through their attitude, they will be themselves degraded and discarded. As used here, "offspring," or "descendants," is a reference to future priests. So, this threat is aimed at both the current priesthood and the priests yet to come. According to Old Testament law, priesthood was reserved for the tribe of Levi, so there is a genetic component as well. The actions of a culture's spiritual leaders will always affect future generations.

When animals were brought for sacrifice, not all of the organs were considered fit for offering. Hunters, butchers, and others who slaughter animals know that some parts are "waste" products which are usually discarded. Even though the priests have been offering ritually impure animals, they would still have been rejecting bits of them as part of the sacrificial process. Here, Malachi is referring to this very debris: the Hebrew word pe'res is often translated as "manure" or "dung," but has a more general meaning of "animal waste."

The symbolism is clear: God will humiliate the Levitical priesthood as plainly as if He'd smeared their faces with filth. God will discard what is unclean and impure, and won't allow it to be used in His temple. This, just as a priest discards the disgusting and unclean animal wastes and doesn't use them as part of worship.