1 Corinthians 2:16 (KJV)

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.

Now we have received, not the spirit of the world, but the spirit which is of God; that we might know the things that are freely given to us of God.

Which things also we speak, not in the words which man's wisdom teacheth, but which the Holy Ghost teacheth; comparing spiritual things with spiritual.

But the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned.

But he that is spiritual judgeth all things, yet he himself is judged of no man.