He is wise in heart, and mighty in strength. The sense is strengthened if we omit "he is," and render, Wise in heart, and mighty in strength, who hath hardened' etc.? God's combination of perfect wisdom with infinite strength renders it hopeless for any man to contend with him.
Who hath hardened himself against him; and hath prospered? Job fully admits the wisdom of all that Eliphaz (Job 4:17) and Bildad (Job 8:3-6) have said, or hinted, with respect to his inability wholly to justify himself.
No one has ever taken this line of absolute self-justification, and prospered.