And they shall kill him, and the third day he shall be raised again - See Matthew 12:40. Mark and Luke add that they understood not that saying, and it was hid from them, and they were afraid to ask him. The reasons of this may have been,
1. They were strongly attached to him, and were exceedingly sorry (Matthew) at any intimation that he was soon to leave them. They learned with great slowness and reluctance, therefore, that he was to be treated in this manner.
2. They were not willing to believe it. They knew that he was the Messiah, but they supposed that he was to be a distinguished prince, and was to restore the kingdom to Israel, Acts 1:6. But to be betrayed into the hands of his enemies, and be put to death, appeared to them to be frustrating all these expectations.
3. Though what he said was plain enough, yet they did not understand it; they could not see how he could be the Messiah, and yet be put to death in this manner; nor did they understand it fully until after the resurrection.

They were exceeding sorry - Since the conversation on the mount, with Moses and Elijah; Peter, James, and John could have no doubt that their Lord and Master must suffer, and that it was for this end he came into the world; but, while they submitted to the counsel of God, their affection for him caused them to feel exquisite distress.

And they shall kill him,.... Put him to death, with the death of the cross; for the angels in rehearsing these words, affirm, that Christ told his disciples at this time, and in this place, whilst they were in Galilee, that he should be crucified, Luke 24:7.
And the third day he shall be raised again: this he said for their comfort; and it is observable, that when Christ speaks of his rising again, he makes mention of the exact time, the third day, on which he should rise, according to the types and prophecies of the Old Testament:
and they were exceeding sorry: that he should be betrayed into the hands of the Gentiles, fearing that another nation would come, and take away, and possess the worldly kingdom and grandeur they were dreaming of; and that he should die at all; and much more that he should die such a cruel and ignominious death, as that of the cross. They seem to have overlooked, and to have taken no notice of his rising again from the dead; which might have administered comfort to them, and have relieved them under their melancholy apprehensions of things; but this they understood not, nor indeed truly any part of what he had said; so Mark and Luke intimate: but then it may be said, how came they to be so very sorrowful, if they did not know what was said? To which may be replied, that this might be the reason of their sorrow, because they did not understand what he said, and they were afraid to ask; they could not tell how to reconcile the betraying of him into the hands of men, and his sufferings and death, with their notions, that the Messiah should abide for ever, and should set up a temporal kingdom, in great splendour and magnificence; and what he meant by rising again from the dead, they could not devise; they could not tell whether all this was to be understood in a literal, or mystical sense.

They were exceeding sorry. Because he said that he must be put to death. There is only grief now, but no remonstrance.