Cross reference
Proverbs 20:5
5 Counsel in the heart of man is like deep water; But a man of understanding will draw it out.
Proverbs 18:4
4 The words of a man's mouth are like deep waters. The fountain of wisdom is like a flowing brook.
Psalms 64:6
6 They plot injustice, saying, "We have made a perfect plan!" Surely man's mind and heart are cunning.
1 Corinthians 2:11
11 For who among men knows the things of a man, except the spirit of the man, which is in him? Even so, no one knows the things of God, except God's Spirit.