“witness of Belial.” A witness in league with Belial, the Devil. For more on Belial, see commentary on 1 Sam. 2:12. Although most versions say “worthless witness,” or “corrupt witness,” or something similar, treating “worthless” as an adjective, the word beliya`al (#01100 בְּלִיַּ֫עַל) is a singular noun. The Hebrew reads, “a witness of Belial.”
“devours.” The Hebrew verb is bala (#01104 בָּלַע), and means to swallow down, but in the piel aspect (the intensive form of the verb) it is intensified, and means to gulp down or devour greedily. This proverb has several interpretations. The wicked gulp down their lies [and the lies of others] as if they were tasty morsels, they do not choke on their lies. These people can look you in the eye and lie in a way that no one would ever suspect it. Also, “wickedness” is put by the figure metonymy for all the food and other good things that criminals get as a result of lying and winning (cp. 4:17; Job 20:12). Also, by gulping down wickedness, they seem to make it disappear. Good liars are now called “spin doctors,” who make good seem evil and evil seem good. That kind of thing has been going on for millennia (cp. Isa. 5:20-24).