John Gill's Exposition of the Whole Bible
Job 20:12
Though wickedness be sweet in his mouth,.... Which may respect some particular sin, and by the context it seems to be the sin of covetousness, or of getting riches in an unlawful way, which is very sweet and pleasing to wicked men, while they are in such pursuits that succeed; and so Mr. Broughton renders it by "wrong"; though it may be applied to sin in general, which is "wickedness", or an evil q, being contrary to the pure and holy nature, will, and law of God; and it is evil in its effects on men, it having deprived them of the image and glory of God, and exposed them to his wrath, to the curses of his law, and to eternal deaths. Now this is "sweet" to an unregenerate man, who minds and savours the things of the flesh, whose taste is not changed, but is as it was from his birth, and who calls sweet bitter, and bitter sweet; such a man has the same delight in sin as a man has in his food, drinks up iniquity like water, and commits sin with greediness; for it is natural to him, he is conceived, born, and brought up in it; besides, some sins are what are more particularly called constitution sins, which some are peculiarly addicted to, and in which they take a peculiar delight and pleasure; these are like the right hand or right eye, and they cannot be persuaded, at any rate, to part with them:
[though] he hide it under his tongue; not for the sake of concealing it, nor by denying, dissembling, or excusing it, but for the sake of enjoying more pleasure in it; as a gluttonous man, when he has got a sweet morsel in his mouth, do not let it go down his throat immediately, but rolls it under his tongue, that he may have all the pleasure of it he can; so a wicked man devises sin in his heart, keeps it on his mind, revolves it in his thoughts, and his meditation on it is sweet; and he is so far from hiding it from others, that he openly declares it, freely tells of it, and takes pleasure in so doing: "fools make a mock at sin"; it is their diversion and recreation.
q רעה "malum", Pagninus, Montanus, Junius Tremellius, Piscator, c.