Ellicott's Commentary for English Readers - John 12:39
(39) 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.... read more
Ellicott's Commentary for English Readers - John 12:38
(38) That the saying of Esaias the prophet might be fulfilled.—This is the first instance in this Gospel of a phrase familiar to us already from its frequent occurrence in St. Matthew. We shall find it again in John 13:18; John 15:25; John 17:12; John 18:9; John 18:32; John 19:24; John 19:36. Its frequency is one of the characteristics of the two Gospels which are most allied to Hebrew modes of thought. St. Matthew and St. John both regard the events of our Lord’s life as fulfilling the... read more