Gregory the Great

But it is one thing to show mercy for sins, another to sin for the sake of showing mercy, which cannot really be called mercy since it does not issue in sweet fruit, since it is embittered through the influence of a diseased root. For here the Lord rebukes such sacrifices through the prophet, saying, "I, the Lord, love justice and hate robbery with whole burnt offerings." … Such people also often withdraw from the poor what they give to God. But the Lord shows how strongly he disowns and censures such conduct.