Albert Barnes Commentary Proverbs 20:17

"Bread of falsehood is sweet to a man; But afterwards his mouth shall be filled with gravel." — Proverbs 20:17 (ASV)

“To eat gravel” was a Hebrew phrase (Lamentations 3:16), and is an Arabic phrase for getting into trouble. So “bread,” got by deceit, tastes sweet at first, but ends by leaving the hunger of the soul unsatisfied. There is a pleasure in the sense of cleverness felt after a hard bargain or a successful fraud, which must be countered by urging people to consider the later consequences.