The Resurrection is the Kingdom of God
Jesus predicted that some of his disciples wouldn't die until they saw the kingdom of God (Mark 9:1). As far as Mark is concerned, that prophecy began to be fulfilled just "six days later" when Jesus was transfigured before three of the twelve. Jesus was radiant that day, all white and sparkly. Indeed, the metamophosis of Jesus was (in the words of Richard Hays) a "sneak preview of Easter." Glorious. Brilliant. Shining. A shade of white no laundry could produce (no kidding, Mark).
I think it's significant that Jesus said some of his disciples wouldn't die until they saw the glory of the kingdom. He didn't use any other benchmark for life. "I tell you, some of you won't get married until . . . some of you won't leave the country until . . . some of you won't observe another seder until . . ." No. It was the terminus of life--death itself--which hung over all their heads like a guillotine. And, ironically, it would be the death of Jesus that would bring about the end of death's reign. For, when Christ was raised from the dead, the glory of God's kingdom was revealed. Jesus killed death, our greatest enemy, so that life would reign forevermore.
In Mark's gospel, the disciples never got to see the fulfillment of that prophecy. All they had to go on was what they heard: Christ is risen and he goes ahead to meet you, "just as he said he would." And so it is.