John 9:33

If this man were not of God, he could do nothing.

The saying is the true testimony of the man born blind that Jesus is from God, reasoning that He had opened his eyes and that without God He could do nothing. The blindness healed was congenital, lifelong blindness from birth, and opening the eyes of one born blind was a thing never heard since the world began, so the extraordinary miracle testifies to divine power and to the truth of His mission. Such a work can be done only by one who worships God and does His will, so Jesus could do nothing apart from God and without God's power.

The man did not yet know Jesus' identity when he was healed, and Jesus later revealed Himself to him as the Son of God, whom the man worshiped. The blind man given sight was a sheep wandering far from the fold, sought by Christ as the compassionate Shepherd with the sympathy of all heaven enlisted for him, and Christ's power to heal him proves Christ is of God and eager to save him. The miracle is wonderful and decisive evidence for the truth of Christ's mission and against the claim that Jesus is a sinner, and the man's reasoning left His opponents unable to answer.

The Jewish leaders and Pharisees are thereby exposed as spiritually blind, hardened by prejudice, unbelief and jealousy. They were jealous of His popularity and miracles, hated Him because He would not receive their ideas, feared He would be honored above them, and in their self-righteousness were not working in harmony with God but uniting with the adversary of God and man and despising the purchase of His blood. They rejected this evidence, made no effort to receive enlightenment but chose to remain in darkness, met the healed man with sneers, hatred and contempt, tried to smother his testimony and close his eyes as they closed their own, and cast him out, thereby making themselves even more spiritually blind.