SEV Biblia, Chapter 17:23
Y le matarn; mas al tercer día resucitar. Y ellos se entristecieron en gran manera.
Clarke's Bible Commentary - Matthew 17:23
Verse 23. 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.
Matthew Henry Commentary
Verses 22, 23 - Christ perfectly knew all things that should befall him, yet undertoo the work of our redemption, which strongly shows his love. What outwar debasement and Divine glory was the life of the Redeemer! And all his humiliation ended in his exaltation. Let us learn to endure the cross to despise riches and worldly honours, and to be content with his will.
Greek Textus Receptus
και 2532 CONJ αποκτενουσιν 615 5692 V-FAI-3P αυτον 846 P-ASM και 2532 CONJ τη 3588 T-DSF τριτη 5154 A-DSF ημερα 2250 N-DSF εγερθησεται 1453 5701 V-FPI-3S και 2532 CONJ ελυπηθησαν 3076 5681 V-API-3P σφοδρα 4970 ADV
Robertson's NT Word Studies
17:23 {And they were exceeding sorry} (kai elupeqesan sfodra). So they at last understood that he was talking about his death and resurrection.