“The earliest Christian Church was a missionary Church. If Christianity ever settles down to be the religion merely of one nation or of one group of nations, it would have become entirely untrue to the tradition which was established for it at the beginning. There was evidently a tremendous urge among those early Christians to carry their message to the ends of the earth. What, then, was the mission of that missionary Church?
What was the Christianity that it propagated in that ancient Roman world?
In the first place, the Christianity that it propagated did not present itself as a new religion. On the contrary, it appealed to an ancient revelation; and it claimed to stand in the full continuity of an age-long plan of God. It should never be forgotten– though it often is forgotten — that the Christian Church at the very beginning had a Bible. Its Bible was the Old Testament; and it regarded that Bible as the Word of God, just as Bible believing Christians regard the Scriptures of the Old and New Testaments today.
In so regarding the Old Testament, it was in exact accord with the Person Whom it presented as the foundation of its life — namely, Jesus Christ ” (149).
“The early Christian church was radically doctrinal. It proclaimed facts: the facts about God the Father, the facts about mankind lost in sin, the facts about Jesus Christ. That is true not merely of Paul but of the very earliest Church in Jerusalem, whose message Paul reproduces for us when be tells us at the beginning of the fifteenth chapter of 1 Corinthians what he had “received” (153 Ch: The Christian View of Missions).
Machen, J. Gresham, edited by Ned Stonehouse “What is Christianity: A Selection of Notable Addresses by a Noble Defender of the Faith” First published in 1951