Therefore they could not believe. For again Isaiah said,
39. Therefore they could not believe. This is somewhat more harsh; because, if the words be taken in their natural meaning, the way was shut up against the Jews, and the power of believing was taken from them, because the prediction of the prophet adjudged them to blindness, before they determined what choice they should make.
We have here the honour done to our Lord Jesus by the Old Testament prophets, who foretold and lamented the infidelity of the many that believed not on him. It was indeed a dishonour and grief to Christ that his doctrine met with so little acceptance and so much opposition; but this takes off the wonder and reproach, makes the offence of it to cease...
Commenting on John 12:37-41
He hath blinded their eyes, and hardened their heart,.... It is of no great moment, whether the he, who is said to blind and harden, be God or Christ, or whether the words be rendered, "it hath blinded", &c. that is, malice or wickedness; or whether they be read impersonally, "their eyes are blinded", &c.