Psalms 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. (Verses like Psalms 64:6)
Proverbs 18:4 - The words of a man's mouth are as deep waters, and the wellspring of wisdom as a flowing brook. (Verses like Proverbs 18:4)
1 Corinthians 2:11 - For what man knoweth the things of a man, save the spirit of man which is in him? even so the things of God knoweth no man, but the Spirit of God. (Verses like 1 Corinthians 2:11)