Albert Barnes Commentary Proverbs 21

Rivers of water - See the Psalms 1:3 note. As the cultivator directs the stream into the channels where it is most wanted, so Yahweh directs the thoughts of the true king, that his favors may fall, not at random, but in harmony with a divine order.

Compare the marginal reference. The words have a special significance as coming from the king who had built the temple, and had offered sacrifices that could not be numbered for multitude (1 Kings 8:5).

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.

Here diligence is opposed, not to sloth but to haste. Undue hurry is as fatal to success as undue procrastination.

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.”