Matthew 17:22

They were troubled exceedingly, not being able to comprehend the mystery of Christ's sufferings and death, which were so opposite to the nations they had of the glorious kingdom of the Messias. (Witham) --- This grief was the consequence of their attachment to their divine Master. They were ignorant, as St. Mark and St. Luke notice, of the word that was spoken. They full well understood that he would be put to death, but did not sufficiently comprehend the shortness of his rest in the grave, the nature of his triumphant resurrection, nor the inestimable benefits which his death would bring on the world. (St. John Chrysostom, hom. lix.)