Summary: The exhortation to Watch must be balanced with the command to Occupy (do business) until I come.
THE ASCENSION OF JESUS
The Acts of the Apostles is a continuation of the account of The Gospel According to Luke. There is a definite continuity between the two books. Both books are addressed to someone called Theophilus, and in the beginning of Acts the evangelist again explains the purpose of his former treatise. The first few verses of Acts fill in some of the apparent gaps between Easter Sunday and the ascension, which were otherwise lacking at the end of Luke 24.
First of all Luke explains the historical limit of his former work: it contained the beginning of the work and teaching of Jesus until the ascension (Acts 1:1). Therefore this second book is the account of the continuation: it contains what Jesus afterwards said and did by the power of the Holy Spirit in the ministry of His Apostles.
Next Luke gives special mention of the activity of Jesus immediately prior to His ascension (Acts 1:2): He gave specific instructions “through the Holy Spirit” to His chosen Apostles. In Luke 24 He had opened up the Old Testament Scriptures to them in such a way as to show them the things pertaining to Himself. Now in Acts 1 He instructed them to return to Jerusalem and await the empowering of the Holy Spirit, after which they were to begin to fulfil the Great Commission.
Then Luke mentions that there were several appearances of Jesus after His resurrection, “with many infallible proofs” over the course of “forty days”, teaching His disciples of “the things pertaining to the kingdom of God” (Acts 1:3). Luke 24 is written in a style which moves swiftly from the resurrection to the ascension almost as if both events had taken place in a single day, but Luke is perfectly clear in Acts 1 that there was the passage of forty days between.
At the end of the forty days, Jesus instructed His disciples to remain in Jerusalem to await the Promise of the Father (Acts 1:4). “Tarry in the city of Jerusalem until you are endued with power from on high” (Luke 24:49).
It must have seemed an age ago that John the Baptist had predicted, “I indeed baptise you with water; but One mightier than I is coming, whose sandal strap I am not worthy to loose. He will baptise you with the Holy Spirit and fire” (Luke 3:16). Now at last the moment drew nigh: the disciples would be “baptised with the Holy Spirit not many days from now” (Acts 1:5).
For a long time Israel's hope had been placed in a Messiah who would be a Maccabean type King who would vanquish the occupying Romans from Israel. This was a teaching which the Apostles had apparently not yet unlearnt. They asked the Lord if He was about to restore the kingdom to Israel (Acts 1:6). It is so easy to become preoccupied with our political present, and thereby to lose sight of the spiritual nature of Christ's kingdom.
Jesus had to remind them, “It is not for you to know times or seasons which the Father has put in His own authority” (Acts 1:7). This echoes part of Jesus' answer to a previous question (Matthew 24:3). “But of that day and hour no one knows, not even the angels of heaven, (nor the Son), but My Father only” (Matthew 24:36).