Albert Barnes Commentary Proverbs 21:6

"The getting of treasures by a lying tongue Is a vapor driven to and fro by them that seek death." — Proverbs 21:6 (ASV)

Vanity - Or, “a breath driven to and fro of those that are seeking death.” Another reading of the last words is: “of the snares of death” (Compare to 1 Timothy 6:9). Some commentators have suggested that the “vapor” or “mist” is the mirage of the desert, misleading those who follow it, and becoming a “net of death.”