John 12:40

40. He hath blinded their eyes They had shut themselves in, and the harder He pushed the tighter the door was pressed. They had made their choice; and the more he would persuade, the more firmly they braced themselves against him. They fitted their eyes to the darkness; and, like owls, the clearer the light the more total their blindness. So that although God, according to the prophet, was the unwilling cause of their blindness, yet it was their wicked will that gave to the cause its effect.

And be converted Which was the desired result on the part of God. But their perverse will transformed his mercy into judgment; his means of softening into results of hardening. Thus does the same sun that melts the wax harden the clay. But the clay is inanimate and blameless; these living agents, hardened by the divine softenings, were free and responsible. The Evangelist has no idea of the modern argument, that because the Jews did not believe the miracles were not real. On the contrary, their unbelief, being a fulfilment of prophecy, was an actual proof of their supernatural reality. That unbelief was by God foreseen, and by him provided for and predicted. Knowing what the Jews would freely do, God had accordingly adjusted his plans, plans contingent indeed upon their doing, yet certain because that doing was freely certain and foreseen Jewish rejection, according to prophecy, is good proof of the reality of Jesus’s Messiahship.