The following is taken from The Believer’s Bible Commentary by William MacDonald, Thomas Nelson Publishers, 1995. All scripture references are from the book of Acts.
Paul’s preaching on Mars Hill (Acts 17:22) is an illustration of the unconventional places in which the early believers preached the Word.
The open air was a favorite. At Pentecost the message may have been preached out of doors, judging from the number who heard and were saved (Acts 2:6, 41). Other general instances of open-air preaching are found in 8:5, 25, 40; 13:44; 14:8-18.
The environs of the temple echoed with the message on at least three occasions (3:1-11; 5:21, 42). Paul and his associates spoke the Word by the riverside in Philippi (16:13). In Athens he preached in the marketplace (17:17) before the address on Mars Hill. In Jerusalem he addressed an angry mob from the stairs of the fortress of Antonia (21:40—22:21).
At least four times the message was declared before the Jewish Sanhedrin: by Peter and John (4:8, 19); by Peter and the other apostles (5:27-32); by Stephen (7:2053); and by Paul (22:30—23:10). Paul and his associates habitually preached the gospel in the synagogues (9:20; 13:5, 14; 14:1; 17:1, 2, 10, 17; 18:4, 19, 26; 19:8).
Private homes were used repeatedly. Peter preached in Cornelius’ house (10:22, 24). Paul and Silas witnessed in the home of the Philippian jailer (16:31, 32). In Corinth Paul preached in the house of Crispus, the ruler of the synagogue. He preached till midnight in a private house in Troas (20:7). He taught from house to house in Ephesus (20:20) and in his own hired house in Rome (28:30, 31).
Philip preached to an Ethiopian eunuch in a chariot (8:31-35), and Paul preached on board a ship (27:21-26). At Ephesus he reasoned daily in a schoolroom (19:9).
Paul preached in civil courts before Felix (24:10), Festus (25:8), and Agrippa (26:1-29).
In 8:4 we read that the persecuted believers went everywhere preaching the Word.
It shows that they did not think the proclamation of the message should be confined to some specially “consecrated” building. Wherever there were people, there was both reason and opportunity for making Christ known. . . . .
We might add that most of the preaching in Acts was spontaneous and extemporaneous. Usually there wasn’t time to prepare a message. “It was not the performance of an hour but the preparation of a lifetime.” It was the preachers who were prepared, not the sermons.