Albert Barnes Commentary Malachi 2:13

"And this again ye do: ye cover the altar of Jehovah with tears, with weeping, and with sighing, insomuch that he regardeth not the offering any more, neither receiveth it with good will at your hand." — Malachi 2:13 (ASV)

And this you have done again - adding the second sin of cruelty to their wives to taking foreign women; they covered the altar of God with tears, in that they by ill-treatment occasioned their wives to weep there to God; and God regarded this, as though they had stained the altar with their tears.

Insomuch that He regardeth not the offering any more - God regarded the tears of the oppressed, not the sacrifices of the oppressors. He would not accept what was thus offered Him as something well-pleasing to Him, acceptable to win His good pleasure.