Though he spare it - That is, though he retains it long in his mouth, that he may enjoy it the more.
And forsake it not - Retains it as long as he can.
But keep it still within his mouth - Margin, as in Hebrew "in the midst of his palate." He seeks to enjoy it as long as possible.

Though he spare it,.... Not that he feeds sparingly on it, for he eats of it freely and plentifully, with great eagerness and greediness; it designs the gratefulness of it to him; he does not spit it out as loathsome, having tasted of it, but retains it as sweet and pleasant; he spares it as Saul did Agag, and as a man spares his only son; sin being a child, a brat of a wicked man, and therefore it is dear unto him:
and forsake it not: as he never will, until he is fully convinced of the evil of it, and it becomes exceeding sinful to him, and so loathsome and disagreeable; and he is restrained from it by the grace of God, and enabled by it to desert it, for such an one only finds mercy, Proverbs 28:13;
but keep it still within his mouth; like an epicure, that will not suffer his food quickly to go down his throat into his stomach, that he may have the greater pleasure in tasting, palating, and relishing it; as Philoxenus, who wished his throat as long as a crane's, that he might be the longer in tasting the sweetness of what he ate and drank; so the wicked man keeps sin within his mouth, not by restraining his mouth from speaking evil, rather by a non-confession of it, but chiefly by continuing and persisting in it, that he might have all the pleasure and satisfaction he has promised himself in it.