Jesus is preparing his disciples to stand firm in the catastrophe which is coming to ancient Israel, especially Jerusalem and her temple. They must see, in those future days, that he has ascended to rule from above and is building a kingdom for God using the power of heaven. The assurance of that is the Christian’s comfort in all times of crisis. But we must add to it the thought of the Lord’s return from that throne, to judge the world and rebuild the cosmos. We don’t know when that will be so we must live faithful to him, as though he could be here at any moment.
And here is a short talk based on the same passage: He Changed The World (Episode 57)