Matt. XX. 17-19.
“And Jesus going up to Jerusalem took the twelve disciples apart in the way, and said unto them, Behold, we go up to Jerusalem; and the Son of Man shall be betrayed unto the chief priests and unto the Scribes, and they shall condemn Him to death, and shall deliver Him to the Gentiles to mock, and to scourge, and to crucify Him; and the third day He shall be raised.”
He goes not up at once to Jerusalem when He has come out of Galilee, but having first wrought miracles, and having stopped the mouths of Pharisees, and having discoursed with His disciples of renouncing possessions: for, “if you will be perfect,” says He, “sell that you have:” and of virginity, “He that is able to receive, let him receive it:” and of humility, “For except ye be converted, and become as little children, you shall not enter into the kingdom of Heaven:” and of a recompense of the things here, “For whoso has forsaken houses, or brethren, or sisters, shall receive an hundredfold in this world:” and of rewards there, “For he shall also inherit,” it is said, “eternal life:” then He assails the city next, and being on the point of going up, discourses again of His passion. For since it was likely that they, because they were not willing this should come to pass, would forget it, He is continually putting them in remembrance, exercising their mind by the frequency with which He reminded them, and diminishing their pain.
But He speaks with them “apart,” necessarily; for it was not meet that His discourse about these things should be published to the many; neither that it should be spoken plainly, for no advantage arose from this. For if the disciples were confounded at hearing these things, much more the multitude of the people.
What then? Was it not told to the people? You may say. It was indeed told to the people also, but not so plainly. For, “Destroy,” says He, “this Temple, and in three days I will raise it up;” and, “This generation seeks after a sign, and there shall no sign be given it, but the sign of Jonas;” and again, “Yet a little while am I with you, and you shall seek me, and shall not find me.”
But to the disciples not so, but as the other things He spoke unto them more plainly, so also spoke He this too. And for what purpose, if the multitude understood not the force of His sayings, were they spoken at all? That they might learn after these things, that fore-knowing it, He came to His passion, and willing it; not in ignorance, nor by constraint. But to the disciples not for this cause only did He foretell it; but, as I have said, in order that having been exercised by the expectation, they might more easily endure the passion, and that it might not confound them by coming upon them without preparation. So for this cause, while at the beginning He spoke of His death only, when they were practised and trained to hear of it, He adds the other circumstances also; as, for instance, that they should deliver Him to the Gentiles, that they should mock and scourge Him; as well on this account, as in order that when they saw the mournful events come to pass, they might expect from this the resurrection also. For He who had not cloaked from them what would give pain, and what seemed to be matter of reproach, would reasonably be believed about good things too.
But mark, I pray you, how with regard to the time also He orders the thing wisely. For neither at the beginning did He tell them, lest He should disquiet them, neither at the time itself, lest by this again He should confound them; but when they had received sufficient proof of His power, when He had given them promises that were very great concerning life everlasting, then He introduces also what He had to say concerning these things, once and twice and often interweaving it with His miracles and His instructions.
But another evangelist says, that He brought in the prophets also as witnesses; and another again says, that even they themselves understood not His words, but the saying was hid from them, and that they were amazed as they followed Him.
Surely then, one may say, the benefit of the prediction is taken away. For if they knew not what they were hearing, neither could they look for the event, and not looking for it, neither could they be exercised by their expectations.
But I say another thing also more perplexing than this: If they did not know, how were they sorry. For another says, they were sorry. If therefore they knew it not, how were they sorry? How did Peter say, “Be it far from You. This shall not be unto You?”
What then may we say? That He should die indeed they knew, albeit they knew not clearly the mystery of the Incarnation. Neither did they know clearly about the resurrection, neither what He was to achieve; and this was hid from them.
For this cause also they felt pain. For some they had known to have been raised again by other persons, but for any one to have raised up himself again, and in such wise to have raised himself as not to die any more, they had never known.
This then they understood not, though often said; nay nor of this self-same death did they clearly know what it was, and how it should come on Him. Wherefore also they were amazed as they followed Him, but not for this cause only; but to me at least He seems even to amaze them by discoursing of His passion.
Source: Homilies on the Gospel of St. Matthew (New Advent)