This and the three following verses are concerned with the case of the evil man. An ungodly man—a man of Belial—diggeth up evil. A man of Belial (Proverbs 6:12) is a worthless, wicked person, what the French call a vaurien. Such a one digs a pit for others (Proverbs 26:27; Psalms 7:15), devises mischief against his neighbour, plots against him by lying and slandering and overreaching. Wordsworth confines the evil to the man himself; he digs it as treasure in a mine, loves wickedness for its own sake. But analogy is against this interpretation. Septuagint, "A foolish man diggeth evils for himself." So Ec Proverbs 27:26, "Whoso diggeth a pit shall fall therein; and he that setteth a trap shall be taken therein." As the gnome says—
ἡ δὲ κακὴ βουλὴ τῷ βουλεύσαντι κακίστη.
And in his lips there is as a burning fire (Proverbs 26:23) His words scorch and injure like a devouring flame. James 3:6, "The tongue is a fire: the world of iniquity among our members is the tongue, which defileth the whole body, and setteth on fire the wheel of nature, and is set on fire by hell." Septuagint, "And upon his lips he treasureth up fire."