Proverbs are notoriously difficult to translate and Prov 18:4 is no exception. One of the main problems here is the complete lack of verbs in the Hebrew which makes it like some of the old Latin proverbs such as: "Mala gallina malum ovum" = bad hen bad egg.
In the Hebrew, the verse reads:
Deep waters words of the mouth; man flowing brook well-spring of
Most versions translate this a simple duplex parallelism something like the NASB:
The words of a person’s mouth are deep waters; The fountain of wisdom
is a bubbling brook.
One of the great things about proverbs is their simultaneous brevity and ambiguity. In this case, it is not clear whether we should read this as an example of synthetic parallelism or antithetical parallelism. That is, are we reading about the same thing expressed in two different ways or are we reading about a contrast. Good arguments could be made both ways.
In any case, the metaphor is clear - wisdom is equated/compared to a flowing stream.
If we understand the proverb as saying the same thing twice using different words then we have the following:
- "words of a man" is parallel to "fountain of wisdom"
- "deep waters" is parallel to "bubbling brook"
In support of this view, Ellicott and Benson agree. For example, Benson says:
Proverbs 18:4. The words of a man’s mouth — Of a wise man’s; are as
deep waters — Full of deep wisdom; and the well-spring of wisdom as a
flowing brook — That wisdom which is in his heart is continually
pouring forth wise and good counsels.
Contrast or Antithetical Parallelism
If we understand the two halves the proverb as presenting a contrast, then we arrive at a totally different understanding:
- "words of a man" is the opposite to "fountain of wisdom" suggesting men are sinful in their speech, compare Rom 3:13, Ps 5:9, 140:3, etc.
- "deep waters" is the opposite to a shallow "bubbling brook" saying that man's sinful practices are deeply embedded.
In support of this view, Barnes says:
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; Psalm 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.
I do not believe we need to finally decide between these two as both can be correct.