This similarity between the two has led to the popular theory that Luke and Matthew shared a common source which was available to both.
For instance, historically reliable information indicates one of the bishops of the early church, Polycarp was well into his 80s when martyred in 156 AD.Augustus Caesar (63 BC – 14 AD), the Roman emperor who reigned during Jesus’ birth, lived to be 76 years old while his successor Tiberius Caesar Augustus (42 BC – 37 AD) died a natural death at age 78.This former book mentioned by the author is clearly the gospel of Luke, that starts with:“Therefore, since I myself have carefully investigated everything from the beginning, it seemed good also to me to write an orderly account for you, most excellent Theophilus, so that you may know the certainty of the things you have been taught.”Both books are addressed to the same Theophilus (literally: “lover of God,” either a real person or a symbolic name for a Christian believer), strongly suggesting Acts is a sequel to Luke.Acts begins where Luke ends, and the style and vocabulary of both books are so similar even the most liberal scholars agree that both books were written by the same person., as the author is not in serious dispute.Only few scholars even attempt to argue that he was not the author.
Let’s look at what we know and notice how all clues point to the conclusion that Luke and Acts were indeed both written by “the beloved physician.”The dates of the synoptic gospels (Matthew, Mark and Luke) are critical because the longer the gap between an event and its record, the more distortion can occur.
Traditionally, therefore, they are referred to as the synoptic gospels Most of the content of 606 out of the 661 verses (approximately 90%) of Mark appears in Matthew.
That means that out of the 1068 verses in Matthew, about 500 (close to half) contain information also found in Mark.
Therefore, the conclusion that Matthew was the author remains somewhat speculative; it is, some might say, a well educated guess.
Let’s look at what we know: This author, at least of an original draft of this book (or one of its major sources), seems quite probably to have been the converted toll collector, also named Levi, who became one of Jesus’ twelve apostles.
Historians consider this the time span following an event during which it can be safely assumed that a significant number of first-hand witnesses are still alive and able to testify.