Acts continues Luke's Gospel
Acts opens as the second part of a two-volume account. Its writer addresses a man called Theophilus and refers back to an earlier book about all that Jesus began to do and teach before his ascension (Acts 1:1-2). Luke's Gospel begins with the same dedication to Theophilus and explains that its author carefully investigated the events surrounding Jesus (Luke 1:1-4).
The matching recipient, style, and opening link show that Luke and Acts belong together. The Gospel tells the story of Jesus' earthly ministry. Acts picks up with the risen Jesus, the coming of the Holy Spirit, and the spread of the good news from Jerusalem outward.
The former treatise have I made, O Theophilus, of all that Jesus began both to do and teach,
Why Luke is the traditional answer
Neither Luke's Gospel nor Acts gives the writer's name in the text itself. Yet from the early centuries of the church, the books were attributed to Luke. The New Testament names Luke as a beloved physician, and Paul includes him among his fellow workers (Colossians 4:14; Philemon 1:24).
Paul also says that Luke was with him during a difficult season near the end of his life (2 Timothy 4:11). This fits the portrait of a careful companion who could report parts of Paul's journeys with first-hand knowledge. The traditional conclusion is not based on one verse that says, “Luke wrote Acts”, but on these connected clues.
Luke, the beloved physician, and Demas, greet you.
The moments when the writer says “we”
Several passages in Acts shift from “they” to “we”. For example, when Paul and his companions sail from Troas towards Macedonia, the narrator includes himself in the journey (Acts 16:10). Similar first-person sections appear later as Paul travels towards Jerusalem and then Rome (Acts 20:5; Acts 27:1).
These passages do not identify the companion by name, so they cannot prove the author was Luke on their own. Still, they make good sense alongside Paul's references to Luke as a faithful co-worker. They also remind us that Acts is not merely a collection of distant stories. Its writer had close contact with the mission he describes.
Why the author matters
Knowing that Acts was likely written by Luke can help you read it as a carefully connected account of Jesus' continuing work. Before Jesus ascends, he tells the disciples that they will be his witnesses from Jerusalem to the uttermost part of the earth (Acts 1:8). Acts then traces that very movement through Peter, Stephen, Philip, Paul, and many unnamed believers.
The main purpose is bigger than settling an author question. Acts points to the risen Christ, the Spirit's power, and a gospel that crosses languages, cities, and social boundaries. Read Acts alongside Luke's Gospel and notice how often the promise of Jesus gives shape to the next step in the story.
But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth.