T the close of chapter 16, we read where Jesus assured His disciples that some of them would see Him "coming in His kingdom" before they tasted death. Just 6 days later Peter, James & John had the privilege of seeing Christ in His glory as He communed with Moses and Elijah on the Mount of Transfiguration. It is reasonable to conclude that this vision was the event of which Christ had spoken when He talked of the disciples seeing Him coming as King. However, even though they saw Elijah in person in their vision, when Jesus spoke of Elijah and how he had arrived previously, these same disciples recognized that He was referring to John the Baptist (vs. 13).
Now, the privileges that Jesus gave to His disciples were certainly not given to them due to any perfection that was in them. Matthew 17:16 indicates that the disciples did indeed have problems with a lack of faith. And yet, they had been chosen by Christ. They were chosen to be leaders in the future. They were chosen to be the recipients of the priviest of all information. Christ shared with them the very story of His own death and resurrection before it even happened (vs. 22-23).
Although Jesus was doing important things like casting out demons and proclaiming the gospel of the kingdom, Matthew 17:27 indicates that He took the time to do “secular” things too, like pay taxes. Perhaps His actions were simply (in part) a product of His compassion for Peter, since he had proclaimed a certain thing concerning Christ and the paying of taxes (vs. 24-25). But if it was for no other reason, this mundane earthly obligation mattered for the sake of obedience to the law and for the testimony of Christ.