Expositor's Bible Commentary Commentary Acts 16:38

"And the sergeants reported these words unto the magistrates: and they feared when they heard that they were Romans;" — Acts 16:38 (ASV)

To beat and imprison a Roman citizen without a trial was a serious offense. So when the magistrates heard that Paul and Silas were citizens, they came to apologize for their illegal actions and to escort them out of prison. Then in order to avoid any further embarrassment or opposition from the crowd, they asked Paul and Silas to leave Philippi. Here was one case where Roman officials took action against the Gospel and its messengers. As such, it seems to run counter to Luke’s apologetic purpose in Acts (cf. Introduction: Luke’s Purposes in Writing Acts). But his point is that the magistrates initially acted in ignorance; and when they came to understand matters more fully, they apologized and did what they could to avoid repetition of the blunder.