Mark 9:30

The dullness of the disciples in spiritual things appears once more, as soon as this announcement was made. There was good in the tidings as well as seeming evil — sweet as well as bitter — life as well as death — the resurrection as well as the cross. But it was all darkness to the bewildered twelve. "They did not understand what He was saying, and were afraid to ask." Their minds were still full of their mistaken ideas of their Master's reign upon earth. They thought that His earthly kingdom was immediately to appear. Never are we so slow to understand, as when prejudice and pre-conceived opinions darken our eyes. The immense importance of our Lord's death and resurrection comes out strongly in this fresh announcement which He makes. It is not for nothing that He reminds us again that He must die. He would have us know that His death was the great end for which He came into the world. He would remind us that by that death the great problem was to be solved — how God could be just, and yet justify sinners. He did not come upon earth merely to teach, and preach, and work miracles. He came to make satisfaction for sin, by His own blood and suffering on the cross. Let us never forget this. The incarnation, and example, and words of Christ, are all of deep importance. But the grand object which demands our notice in the history of His earthly ministry, is His death on Calvary. Let us mark, in the second place, in these verses, the ambition and love of pre-eminence which the apostles exhibited. "By the way they disputed among themselves who was the greatest." How strange this sounds! Who would have thought that a few fishermen and publicans could have been overcome by envious rivalry, and the desire of supremacy?

They - passed through Galilee - See on Mat 17:22-27 (note).