When asked if he was about to restore the Kingdom to Israel, Jesus reminds his disciples that “it is not for them to know” when the kingdom will be restored. Rather than knowing the “times and dates” God has planned, the disciples are to be witnesses to the good news of Jesus in Jerusalem, Judea, Samaria, and all the earth. To some extent, the kingdom is about to begin in the Temple in a manner which is not unlike what many expected. The Holy Spirit will fall upon people and they will speak the Word of God in power in the Temple itself.
These men are to be witnesses, a very important word in Luke-Acts and this command is in many ways programmatic for the chapters which follow. In the chapters which follow, the 12 disciples are called witnesses 8 times, and the Holy Spirit bears witness on their behalf (Acts 5:32). Both Paul (22:15, and 26:16) and Stephen (22:20) are called witnesses in Acts.
The disciples are to give testimony of who Jesus was (the messiah) and what Jesus did (died for the forgiveness of sins) and what he intends to do (return to establish his kingdom). They are all eyewitnesses of the life of Jesus, his death and resurrection, and they will be witnesses to the coming of the Holy Spirit (in Acts 2). They are Jesus’ own personal representatives sent to report to others what Jesus said and did.
As in the modern use of the word, a ‘witness” often functioned in a legal context, giving testimony in a court case. As the disciples give their testimony in various speeches, sermons or other teaching opportunities, they are offering evidence concerning who Jesus is. This evidence can be corroborated other eye-witnesses. In Luke 1:2, the author claims to have done this already, confirming the events of his Gospel by eyewitnesses. That Luke himself is a part of the story after Acts 16 indicates that he is an eyewitness himself and can confirm the truth of his document.
This is an important historical point, since what accounts for evidence for a first century historian differs from that of a modern writer. As Keener points out, to call upon witnesses is common in other Greco-Roman histories. An eyewitness was the most important evidence a writer could give. Polybius, for example claimed that “sight is, according to Heracleitus, by far the truer; for eyes are surer witnesses than ears” (Hist. 12.27). As I suggested in a previous post, Luke can be both historical and theological, since the two are virtually the same in the literary world of the first century.
This commission to be the witnesses of the Messiah in Jerusalem is based on the activity of the Holy Spirit. They are verbally commissioned, but it will be the reception of the Holy Spirit which empowers them to preach and confirms the words of their preaching (through signs and miracles). In another post I wondered a bit about applying Acts to the Mission of the Church in a contemporary context – I think that this idea of witness may be a good place to start. How can we bridge the gap between the first century apostolic witness and our presentation of the gospel in the twenty-first century?