Matthew 17:23

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.