"Parthians, Medes and Elamites; people from Mesopotamia They were convinced by [Peter's] arguments and they accepted what he said and were baptised." (Acts of the Apostles 1:9,41).
If this report is historical, then the earliest account of Mesopotamians and people of the Roman Eastern frontier becoming Christians comes about the year 30-35 CE. The same passage also cites people from " Cappadocia, Pontus and Asia, Phrygia and Pamphilia- These people were probably a mixed group of Jews who had come to Jerusalem to celebrate the wheat harvest feast of Pentecost; and pagan traders. These neophytes would have brought back their new religion back to their own countries, thus accounting for the spread of Christianity on both sides of the Roman Eastern Frontier. There was probably not a systematic evangelisation as there is no mention of Christian growth in most of these regions in the book of Acts; and there is no extra-biblical evidence of how successful these neophytes had spread their religion among their family members. What is interesting in this passage however, is that a mixed group of Jews and Gentiles had come to the Christian belief at the same time, and not as many would believe, the Jews first followed later by the Gentiles.
Hence one of the causes for the spread of Christianity is the movement of traders. The role of traders as early spreaders of religion appears to be a common denominator in Christian proselytising to the east of the Roman Frontier. W.C. McCullough supports this view and posits some of his theories, drawing from examples from the Jews. The Acts of the Holy Apostle Thomas also attribute the saint's mission to India with the help of a merchant. .
In the Book of Revelation's letters to the 7 churches, there are implicit references to Christian traders in Asia Minor ( 2:14, 20; 4:14-18). With the exception of Laodicea, all the other 6 cities mentioned in Revelations were large commercial centres of the Roman empire.