Clearly the actions of the girl"s masters against Paul and Silas, whom the people perceived as Jews, were prejudicial. They wanted to get even for causing them financial loss (cf. Acts 19:24-27), not for preaching the gospel. Normally only wealthy people took the risk of prosecuting someone in court since such action was very expensive. [1] This is the first formal indictment against Paul that Luke recorded in Acts. The market place was the agora. [source][source][source]
"Often, if not always, the greatest obstacle to the crusade of Christ is the selfishness of men." [2][source]
Two magistrates (praetors) governed each Roman colony. [3] Recently the Emperor Claudius had expelled the Jews from Rome ( Acts 18:2). Consequently anti-Semitism was running especially high throughout the empire and in Philippi, which had an unusually large military population. It was contrary to Roman law for local people to try to change the religion of Roman citizens, of which there were many in Philippi. The girl"s masters assumed that Paul and Silas were proselytizing for Judaism since the customs Paul proclaimed included worship of Jesus, a Jew, rather than the emperor. [source][source][source]
"The accusation against Paul and Silas in Acts 16:20-21 is one of a series. In Acts 16-19 we find four scenes that feature accusations against Christians, and these accusations are parts of similar sequences of events. The sequence contains three basic elements: (1) Christians are forcefully brought before officials or a public assembly. (2) They are accused, and this accusation is highlighted by direct quotation. (3) We are told the result of this attempt to curb the Christian mission." [4][source]