Paul’s bringing the gospel to Philippi, early in his second missionary journey (A.D. 49-52), is described in Acts 16. After visiting the churches in Galatia (a Roman province in central Asia Minor) that he’d founded on his first missionary journey, he was prevented by the Holy Spirit from preaching the gospel in Asia or Bithynia (the provinces west and north of Galatia) and ended up in Troas (a seaport). There he had a vision of a man of Macedonia (the province north of Greece) standing and begging him, “Come over into Macedonia and help us.” Concluding that God wanted them to preach the gospel there, Paul and his companions (Silas, Timothy, and Luke) sailed to Macedonia.
Philippi was the first place where they stayed in Macedonia. On the Sabbath they went outside its city walls to a place of prayer (apparently there weren’t enough Jews in Philippi to have a synagogue) beside the river, where they sat down and spoke to the women gathered there. The Lord opened the heart of one of them, Lydia, a Gentile businesswoman who worshipped the Jewish God, to respond to Paul’s message. She and her household were baptized, and she invited Paul and his companions to stay at her house.
However, Paul’s casting out of a slave girl a spirit that had enabled her to predict the future got Silas and him in trouble. The girl’s owners, who had made money from her fortune-telling, charged them before the magistrates with being wandering Jews who were upsetting the city by advocating customs unlawful for Romans. The magistrates had Paul and Silas beaten and thrown into prison. That night, while the two were praying and singing hymns, an earthquake shook the prison. Thinking that the prisoners had escaped the jailer was about to kill himself, but Paul stopped him. As a result, the jailer and his family were saved and baptized.
The next morning, the magistrates sent their officers to release Paul and Silas and expel them from Philippi. Paul protested that as Roman citizens they should not have been beaten and imprisoned without a trial and demanded that the magistrates themselves escort them out. The magistrates did so, requesting Paul and Silas to leave the city. After meeting with and encouraging the Christians at Lydia’s house, Paul and his companions (except Luke, his use of “we” that began in Acts 16:10 ending in 16:17 and not resuming until 20:5) left Philippi.
“Paul and Silas had an extraordinary call to Philippi; and yet, when they have come thither, they see little of the fruit of their labours, and are soon driven thence. Yet they did not come in vain. Though the beginnings here were small, the latter end greatly increased [Job 8:7]; now they laid the foundation of a church at Philippi, which became very eminent, had its bishops and deacons, and people that were more generous to Paul than any other church, as appears by his epistle to the Philippians, ch. i. 1; iv. 25. Let not ministers be discouraged, though they see not the fruit of their labours presently; the seed sown seems to be lost under the clods, but it shall come up again in a plentiful harvest in due time.” (Matthew Henry’s Commentary on the Whole Bible, Old Tappan, New Jersey: Fleming H. Revell Company, Vol. VI, page 217)