I.H. Marshall, Jesus the Savior, IVP, 1990, p. 291ff
"Paul begins here to extend as it were his hand to restrain the audacity of humans, in case they should clamor against God's judgments. We cannot by our own faculties examine the secrets of God, but we are admitted into a certain and clear knowledge of them by the grace of the Holy Spirit. And just as we ought to follow the guidance of the Spirit, so where He leaves us, we ought to stop there and fix our standing.
"If anyone will seek to know more than what God has revealed, he shall be overwhelmed with the immeasurable brightness of inaccessible light. But we must bear in mind the distinction between the secret counsel of God and His will made known in Scripture.
"For though the whole doctrine of Scripture surpasses in its height the mind of man, yet an access to it is not closed against the faithful, who reverently follow the Spirit; but with regard to God's hidden counsel, the depth and height of it cannot be reached."
- John Calvin