Counsel in the heart of man is like deep water; but a man of understanding will draw it out.
Proverbs 18:4 The words of a man's mouth are as deep waters, and the wellspring of wisdom as a flowing brook.
Psalm 64:6 They search out iniquities; they accomplish a diligent search: both the inward thought of every one of them, and the heart, is deep.
1 Corinthians 2:11 For what man knows the things of a man, save the spirit of man which is in him? even so the things of God knows no man...