In his mouth, i.e. to his taste, though it greatly please him for the present. Though he hide it under his tongue; as an epicure doth a sweet morsel, which he is loth to swallow, and therefore keeps and rolls it about his mouth that he may longer enjoy the pleasure of it: though he be highly pleased with his lusts, and cleave to them in hearty love, and resolve to hold them fast, and improve them to the greatest delight and advantage.
Related Commentaries of Job 20:12
Job 20:12
12 Though wickedness be sweet in his mouth, though he hide it under his tongue;