II. The second section (vs. 21-23) contains the startling new revelation of the suffering Messiah, and the disciples' repugnance to it. The Gospel has two parts: Jesus is the Christ, and the Christ must suffer and enter into His glory. Our Lord has made sure that the disciples have learned the first before He leads to the second. The very conviction of His dignity and divine nature made that second truth the more bewildering, but still the only road to it was through the first. Verse 21 covers an indefinite time, during which Jesus gradually taught His sufferings. Ordinarily we exaggerate the suddenness, and therefore the depth, of Peter's fall, by supposing that it took place immediately after his confession; but the narrative discountenances the idea, and merely says that Jesus then 'began' His new teaching. There had been veiled hints of it (such as John ii. 19, and Matt. ix. 15, xii. 40), but henceforward it assumed prominence, and was taught without veil. It was no new thought to Himself, forced on Him by the growing enmity of the nation. The cross always cast its shadow on His path. He was no enthusiast, beginning with the dream of winning a world to His side, and slowly and heroically making up His mind to die a martyr, but His purpose in being born was to minister and to die, a ransom for the many. We have not here to do with a growing consciousness, but simply with an increasing clearness of utterance. Note the detailed accuracy of His prevision, which points to Jerusalem as the scene, and to the rulers of the nation as the instruments, and to death as the climax, and to resurrection as the issue, of His sufferings; the clear setting forth of the divine necessity which, as it ruled all His life, ruled here also, and is expressed in that solemn 'must'; and the perfectly willing acceptance by Him of that necessity, implied in that 'go,' and certified by many another word of His. The necessity was no external compulsion, driving Him to an unwelcome sacrifice, but one imposed alike by filial obedience and by brotherly love. He _must_ die because He _would_ save.