Then the disciples understood that he spoke unto them of John the Baptist.
All Commentaries on Matthew 17:13 Go To Matthew 17
John Chrysostom
AD 407
And after a little while again, when He had cast out the devil, which His disciples were not able to cast out; for then too, As they abode in Galilee, so it says, Jesus said unto them, The Son of Man shall be betrayed into the hands of sinful men, and they shall kill Him, and the third day He shall rise again. Matthew 17:23
Now in doing this, He by the greatness of the miracles was abating the excess of their sorrow, and in every way consoling them; even as here also, by the mention of John's death, He afforded them much consolation.
But should any one say, Wherefore did He not even now raise up Elias and send him, witnessing as He does so great good of his coming? we should reply, that even as it was, while thinking Christ to be Elias, they did not believe Him. For some say, such are the words, that You are Elias, and others, Jeremias. Matthew 16:14 And indeed between John and Elias, there was no difference but the time only. Then how will they believe at that time? it may be said. Why, he will restore all things, not simply by being recognized, but also because the glory of Christ will have been growing more intense up to that day, and will be among all clearer than the sun. When therefore, preceded by such an opinion and expectation, he comes making the same proclamation as John, and himself also announcing Jesus, they will more easily receive his sayings. But in saying, They knew him not, He is excusing also what was done in His own case. Luke 23:24
And not in this way only does He console them, but also by pointing out that John's sufferings at their hands, whatever they are, are undeserved; and by His throwing into the shade what would annoy them, by means of two signs, the one on the mountain, the other just about to take place.
But when they heard these things, they do not ask Him when Elias comes; being straitened either by grief at His passion, or by fear. For on many occasions, upon seeing Him unwilling to speak a thing clearly, they are silent, and so an end. For instance, when during their abode in Galilee He said, The Son of Man shall be betrayed, and they shall kill Him; Matthew 17:22-23 it is added by Mark, That they understood not the saying, and were afraid to ask Him; Mark 9:32 by Luke, That it was hid from them, that they might not perceive it, and they feared to ask Him of that saying. Luke 9:45