10 And, look you! so also say I, that those who have such lofty ideas of themselves as to suppose that so much must be attributed to the powers of their own will, that they deny their need of the divine assistance in order to a righteous life, cannot believe in Christ. For the mere syllables of Christ's name, and the Christian sacraments, are of no profit, where faith in Christ is itself resisted. For faith in Christ is to believe in Him that justifies the ungodly; to believe in the Mediator, without whose interposition we cannot be reconciled unto God; to believe in the Saviour, who came to seek and to save that which was lost; to believe in Him who said, “Without me you can do nothing.” Because, then, being ignorant of that righteousness of God that justifies the ungodly, he wishes to set up his own to satisfy the minds of the proud, such a man cannot believe in Christ.
And so, those Jews “could not believe:” not that men cannot be changed for the better; but so long as their ideas run in such a direction, they cannot believe. Hence they are blinded and hardened; for, denying the need of divine assistance, they are not assisted. God foreknew this regarding these Jews who were blinded and hardened, and the prophet by His Spirit foretold it.
Source: Tractates on the Gospel of John (New Advent)