Charles Ellicott Commentary Proverbs 21:4

"A high look, and a proud heart, [Even] the lamp of the wicked, is sin." — Proverbs 21:4 (ASV)

The plowing of the wicked.— that is, their work, all they do; for it is not done to please God but themselves; nor carried on in His strength, but in reliance upon their own, and therefore it is “sin,” not pleasing to Him. For the word here translated “plowing,” see above on Proverbs 13:23, where it is rendered “tillage.” It may also signify “lamp” (see above on Proverbs 13:9).