C. F. Keil and Franz Delitzsch on Proverbs 10:20

Pro 10:20 20 Choice silver is the tongue of the righteous;      But the heart of the godless is little worth.

Choice silver is, as Pro 8:19, cf. 10, pure, freed from all base mixtures. Like it, pure and noble, is whatever the righteous speaks; the heart, i.e., the manner of thought and feeling, of the godless is, on the contrary, like little instar nihili, i.e., of little or no worth, Arab. yasway kâlyla (Fl.). lxx: the heart of the godless ἐκλείψει, i.e., ימעט, at first arrogant and full of lofty plans, it becomes always the more dejected, discouraged, empty. But 20a leads us to expect some designation of its worth. The Targ. (according to which the Peshito is to be corrected; vid., Levy’s Wörterbuch, ii. 26): the heart of the godless is מחתא (from נחת), refuse, dross. The other Greek versions accord with the text before us.