Though wickedness be sweet in his mouth - Though he has pleasure in committing it, as he has in pleasant food. The sense of this and the following verses is, that though a man may have pleasure in indulgence in sin, and may find happiness of a certain kind in it, yet that the consequences will be bitter - as if the food which he ate should become like gall, and he should cast it up with loathing. There are many sins which, from the laws of our nature, are attended with a kind of pleasure. Such, for illustration, are the sins of gluttony and of intemperance in drinking; the sins of ambition and vanity; the sins of amusement and of fashionable life. To such we give the name of “pleasures.” We do not speak of them as “happiness.” That is a word which would not express their nature. It denotes rather substantial, solid, permanent joy - such joy as the “pleasures of sin for a season” do not furnish. It is this temporary “pleasure” which the lovers of vanity, fashion and dress, seek, and which, it cannot be denied, they often find. As long ago as the time of Zophar, it was admitted that such pleasure might be found in some forms of sinful indulgence and yet even in his time that was seen, which all subsequent observation has proved true, that such indulgence must lead to bitter results.
Though he hide it under his tongue - It is from this passage, probably, that we have derived the phrase, “to roll sin as a sweet morsel under the tongue,” which is often quoted as if it were a part of Scripture. The “meaning” here is, that a man would find pleasure in sin, and would seek to prolong it, as one does the pleasure of eating that which is grateful to the palate by holding it long in the mouth, or by placing it under the tongue.