5 What did the Lord answer to these things? Then says Jesus to them: “My time is not yet come; but your time is always ready.” What is this? Had not Christ's time yet come? Why then was Christ come, if His time had not yet come? Have we not heard the apostle say, “But when the fullness of time came, God sent His Son”? If, therefore, He was sent in the fullness of time, He was sent when He ought to be sent, He came when it behooved that He should come. What means then, “My time is not yet come”?
Understand, brethren, with what intention they spoke, when they appeared to advise Him as their brother. They were giving Him counsel to pursue glory; as advising in a worldly manner and with an earthly disposition, that He should not be unknown to fame, nor hide Himself in obscurity. This is what the Lord says in answer to those who were giving Him counsel of glory, “My time is not yet come;”— the time of my glory is not yet come. See how profound it is: they were advising Him as to glory; but He would have loftiness preceded by humility, and willed to prepare the way to elevation itself through humility.
For those disciples, too, were of course seeking glory who wished to sit, one at His right hand and the other at His left: they thought only of the goal, and saw not by what way it must be reached; the Lord recalled them to the way, that they might come to their fatherland in due order. For the fatherland is on high, the way there lies low. That land is the life of Christ, the way is Christ's death; that land is the habitation of Christ, the way is Christ's suffering. He that refuses the way, why seeks he the fatherland? In a word, to these also, while seeking elevation, He gave this answer: “Can ye drink the cup which I am about to drink?” Behold the way by which you must come to that height which you desire. The cup He made mention of was indeed that of His humility and suffering.
Source: Tractates on the Gospel of John (New Advent)