" (Kummel 148) Luke himself can be considered the author due to the similarity of the authorship in Acts with Paul's allusions to his companions during his state of imprisonment. The major question that is raised is whether the inferred or traditional assumption that Luke the physician is the author of Luke can be connected with the information in Luke and Acts. "In addition, Cadbury showed that almost all of the medical expressions in Luke are to be found in the LXX, Josephus, and Plutarch." (Kummel 148) .
Another view on the authorship of Luke states that the author was clearly not an eyewitness. "He had received information from others who were "eyewitnesses and servants of the word." Moreover, he implies that the earlier narratives were easily accessible to him." (Guthrie 113) We can infer that the author was a cultured man. He was also a careful writer who did not belong to the group of the Lord's followers. .
External testimony assumes common authorship of the gospel and Acts, and it may be maintained that the book of Acts was accepted into the New Testament canon because of its close association with the Gospel of Luke. It is essential to investigate the foundation on which this association may be based. There are five pieces of information that helps us to understand the association between Luke and Acts better. "The first observation is that both books are written by the same author which is Theophilus. A second observation is that Acts refers to the first treatise, which is understood as the gospel. A third observation is the two books have very similar language and style of writing. Fourth, they both have common interests. A fifth observation is Acts naturally continues on from Luke's gospel." (Guthrie 115) However, many scholars have difficulties making a connection between the two gospels.
There is also evidence in Acts that strongly suggests that the author was a companion of the apostle Paul.