The parallelism of the two clauses is probably one of contrast. If so, the proverb is a comparison between all teaching from without and that of the light within. "The words of a man' s mouth" are dark as the "deep waters" of a pool, or tank ("deep waters" being associated in the Old Testament with the thought of darkness and mystery; compare Proverbs 20:5; Psalms 69:2; Ecclesiastes 7:24); but "the wellspring of wisdom is as a flowing brook," bright and clear. The verse presents a contrast like that of Jeremiah 2:13.
Other Barnes' Notes entries containing Proverbs 18:4:
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