For he taught his disciples ( ἐδίδασκε γὰρ τοὺς μαθητὰς αὑτοῦ); literally, for he was teaching (imperfect) his disciples. The Son of man is delivered ( παραδίδοται) The whole is present to his mind, as though it were now taking place.
And they shall kill him ( ἀποκτενοῦσιν). This is a stronger form of κτείνω. And when he is killed, after three days he shall rise again ( ἀναστήσεται); literally, he shall rise up. Our Lord repeats this prediction, in order that, when these events actually took place, his disciples might not be alarmed or offended, or abandon their faith in him, as though he could not be the Messiah because he underwent so terrible a death.
It will be remembered that, notwithstanding these repeated warnings from their Lord, when these events actually took place, "they all forsook him and fled." It was therefore necessary that this coming event of his crucifixion should be repeatedly impressed upon them, that they might thus be assured that he was willing to undergo this bitter death; that he was not going to his cross by constraint, but as a willing Sacrifice, that he might do the will of his Father, and so redeem mankind.
Therefore he repeated all this in Galilee, when he returned from his transfiguration, and after he had cast out the evil spirit from the epileptic child, and so had gained to himself great renown. He would thus restrain the excited feelings of his disciples, and impress upon them the reasons for his journey to Jerusalem, and prepare them for the dread realities which were awaiting him there.