Therefore they could not believe, because. — The words refer to those which have gone before, not to those which follow, and then by an addition give the reason more fully. “It was on account of the divine will expressed in Isaiah’s prophecy.” “It was therefore, namely, because Isaiah said again.”
The words, “they could not believe,” must be taken in their plain meaning as expressing impossibility. The Apostle is looking back upon the national rejection of Christ, and seeks a reason for it. He remembers how our Lord Himself had explained His method of teaching by parables, and has based it upon this prophecy of Isaiah (Matthew 13:14). The principle was that which has been repeated in His last public words (John 12:35-36); that power used is increased, and power neglected destroys itself. Here, then, in these prophetic words was the reason they could not believe. Wilful rejection had been followed by rejection which was no longer within the power of the will. With this statement of St. John’s should be compared our Lord’s words on the same subject in John 5:40; John 6:37, Notes, and St. Paul’s arguments in Romans 9-11.