Albert Barnes 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 - The Hebrew word, with a change in its vowel points, may signify either:

1. the “fallow field,” the “tillage” of Proverbs 13:23, or
2. the lamp.

According to the first option, the verse would mean, “The outward signs of pride, the proud heart, the broad lands of the wicked, all are evil.” The second option, however, belongs, as it were, to the language of the time and of the book (Proverbs 13:9; Proverbs 24:20). The “lamp of the wicked” is their outwardly bright prosperity.