From that time forth began Jesus to show unto his disciples, how that he must go unto Jerusalem, and suffer many things of the elders and chief priests and scribes, and be killed, and be raised again the third day.
All Commentaries on Matthew 16:21 Go To Matthew 16
Jerome
AD 420
But that none should suppose that this is only any explanation, and not an evangelic interpretation, what follows explains the reasons of His forbidding them to preach Him at that time; “Then began Jesus to show unto his disciples that he must needs go unto Jerusalem, and suffer many things of the elders and Scribes, and Chief Priests, and be put to death, and rise again the third day. "The meaning is; Then preach Me when I shall have suffered these things, for it will be of no avail that Christ be preached publicly, and His Majesty spread abroad among the people, when after a little time they shall see Him scourged and crucified.