In Acts 1:1-3, Luke records that the resurrection appearances were spread over a period of 40 days, during which Jesus gave 'many convincing proofs' of his resurrection. However, this series of appearances terminated abruptly with one final, dramatic, departure.
Jesus had apparently been preparing his disciples for this moment: for he had given them instructions on more than one occasion to remain in Jerusalem until they received the power of the Holy Spirit (Lk 24:49, Acts 1:4-8).
Luke 24:50-52 indicates that this final meeting began somewhere in Jerusalem, from where Jesus had led them out towards Bethany. The more detailed account in Acts 1:6-12 indicates that their final destination was the Mount of Olives. During their final conversation Jesus refused to answer questions about the future of Israel. But He again promised that they would soon receive an empowerment from the Holy Spirit that would enable them to be witnesses to Himself throughout the whole world.
After this, the disciples saw him 'lifted up' from the earth until he was hidden from sight by a cloud. While still gazing upward, two 'men dressed in white' appeared, who told them that Jesus would one day return to the earth in the same manner as they had seen Him go.
Many have sought to explain away the resurrection appearances as some form of delusion: but this series of appearances defies such analysis. There is no doubt that the disciples had derived great comfort from them: but if they had been delusional, they would have had a tendency to become more vivid and frequent as time went by. Instead, they stop abruptly at this point. Moreover, such delusions mainly affect individuals, whereas this event was witnessed by at least eleven people, and possibly up to 120 (c.f. Acts 1:12-15). Indeed, nearly all of the appearances were to groups: not individuals.
For there to be any chance of a corporate delusion taking hold, it would have to be something that those involved fundamentally wanted to believe: but that can hardly be said of Jesus leaving his disciples on their own to carry on the work in the very city that had crucified their Master! And yet, Luke 24:52 tells us that they did indeed return to Jerusalem with great joy. As the delusional behaviour of a band of frightened men, it makes no sense: but as the behaviour of a group of men who have spent 40 days in the company of an undeniably resurrected Jesus, who has just promised that they will soon receive all the power they need, it makes very good sense.
What happened next - the miraculous series of events beginning on the day of Pentecost - is outside the scope of this part of our discussion. But as further evidence for the reality of Jesus' resurrection it will warrant very serious examination at a later stage.