In several previous posts (here, here, and here) I addressed the problem of differences in the Gospels, pointing out that what are often taken for contradictions are really just examples of 21st century Westerners trying to impose unrealistic and modern standards of historical reporting on ancient Easterners. I demonstrated this by pointing to examples in which two different passages within the same book report different information. No one thinks of these as being contradictions because they come from the same author, and appear in the same literary document.
I found another example of this, but not in the Gospels this time. This one appears in Acts. Luke’s account of Jesus’ words to Paul on the Damascus road reads as follows: “Saul, Saul, why are you persecuting me? … I am Jesus, whom you are persecuting. But rise and enter the city, and you will be told what you are to do.” (Acts 9:5b-6, ESV)
Paul, recounting the same event in Acts 26:14b-18, records Jesus’ words as:
“Saul, Saul, why are you persecuting me? It is hard for you to kick against the goads. … I am Jesus whom you are persecuting. But rise and stand upon your feet, for I have appeared to you for this purpose, to appoint you as a servant and witness to the things in which you have seen me and to those in which I will appear to you, delivering you from your people and from the Gentiles-to whom I am sending you to open their eyes, so that they may turn from darkness to light and from the power of Satan to God, that they may receive forgiveness of sins and a place among those who are sanctified by faith in me.” (ESV)
Not only is Acts 22 much fuller in its account of what Jesus said to Paul, but there is little overlap between them as it pertains to Jesus’ instructions. In Acts 9 Jesus instructs Paul to go to Damascus and wait to be told what to do. In Acts 22 Jesus does not tell Paul to go to Damascus, but instead, instructs him in his mission on the spot! If these two accounts appeared in two different books, critics would claim a contradiction. But because they appear in the same literary work, no such charge is made.
Of course, a reasonable harmony can be made for the two accounts. Acts 9 appears to be a summary of the much longer conversation, rather than a transcript of the actual words Jesus said (at least for His instructions; not His introduction and self-revelation). Acts 22 is probably closer to an actual transcript of what was said to Paul.
The fact that Jesus discloses to Paul His purpose for his life there on the road does not contradict what Luke reports in chapter 9. No specific instructions were given regarding what he should do next to fulfill that purpose. Furthermore, in the context of Acts 9, it seems what Paul was “to do” in Damascus was receive salvation. That is why the Lord spoke to Ananias in a vision to go pray for Paul to regain his sight and be filled with the Spirit (9:10-19).