9: But as it is written, Eye hath not seen, nor ear heard, neither have entered into the heart of man, the things which God hath prepared for them that love him. 10: But God hath revealed them unto us by his Spirit: for the Spirit searcheth all things, yea, the deep things of God. 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. 12: 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. 13: 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. 14: 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. 15: But he that is spiritual judgeth all things, yet he himself is judged of no man. 16: For who hath known the mind of the Lord, that he may instruct him? But we have the mind of Christ.
Paul quotes Isa 64v4. Paul says that no eye has seen yet nor ear has heard yet nor has it even been thought of, all the things which God has prepared for them that love him, however God has revealed all this unto us by His Spirit because the Spirit completely understands everything even the deepest purposes of God. Who knows a man completely apart from the spirit of that man? In the same way the things of God are not known by man but the Spirit of God knows everything. When we were saved, we did not receive the spirit of the world but the Spirit of God so that we might know the things which have been freely given us of God. We talk about these things not in human wisdom but in the wisdom which is given us of the Holy Spirit. We compare spiritual things with spiritual things. The unbeliever does not receive the things of the Spirit because they are foolishness to him nor can he know them because these things are understood by those that are spiritual. The spiritual man – the Christian who lives by walking in the Spirit, comes to a judgment on all issues yet he is judged of no man. Because who has fully known the mind of the Lord on every issue, that he may instruct him? Those that are spiritual have the mind of Christ.