Heidegger's Bible Handbook: Acts: Argument of the Book

5. The argument of the same. It is a part of the Gospel.

That is, this book relates the beginning of the Church of the New Testament, or of the law going forth from Zion, Isaiah 2:3, and its increase among the Jews, and its enlargement and propagation among the Gentiles, especially toward the West, or the islands of the sea, all the way to Rome, the metropolis of the world, on which, as on a great and high mountain, God willed for the first time to manifest and to administer His Church; the diverse journeys of Saint Paul, who, like a vigorous general, passed over all lands and seas, until the last journey to Jerusalem; and, finally, his afflictions and dangers, which befell him, both in Judea, Jerusalem, and Cæsarea, and in the journey toward Rome on land and sea, and finally in the city of Rome itself. Hence, this history is a part of the Gospel, and not the least. In the Gospel is described the seed sown in the soil; here is described the seed sprouted, and opening and displaying by degrees its powers. But if through Luke we had not learned, in what manner Christ left the earth; when, in what place, and in what manner the promise of the Holy Spirit came; with what origins the Church began; by what means it was polluted; by what means it increased: we certainly would have been ignorant of a great part of the Gospel.

Dr. Dilday's Lecture: "Acts of the Apostles, Part 3"