The Spiritual Man

1 Cor 2:
12 Now we have received not the spirit of the world, but the Spirit who is from God, that we might understand the things freely given us by God.
13 And we impart this in words not taught by human wisdom but taught by the Spirit, interpreting spiritual truths to those who are spiritual.
14 The natural person does not accept the things of the Spirit of God, for they are folly to him, and he is not able to understand them because they are spiritually discerned.
15 The spiritual person judges all things, but is himself to be judged by no one.
16 "For who has understood the mind of the Lord so as to instruct him?" But we have the mind of Christ.

Paul's point here is that no one understands the mind of the Lord let alone is able to "instruct" Him. The Holy Spirit is given to, and indwells those whom Christ died for, i.e. the elect, to whom His righteousness is first imputed; then the indwelling Spirit is given,(regeneration).
Then those who are "spiritual" may discern and understand the mind of Christ.
Therefore, since natural (unregenerate) man cannot instruct (judge) the Lord,then the natural man cannot judge (instruct) those for whom Christ has died, and are born from above by the Spirit (the spiritual), for we are of Christ, and Christ is judged by no man; subsequently, neither are we.

1Cor 1:
30 And because of him you are in Christ Jesus, who became to us wisdom from God, righteousness and sanctification and redemption,
31 so that, as it is written, "Let the one who boasts, boast in the Lord."