Acts 13:15 - Wesley's Explanatory Notes

And after the reading of the law and the prophets, the chief of the synagogue sent to them — The law was read over once every year, a portion of it every Sabbath: to which was added a lesson taken out of the prophets. After this was over, any one might speak to the people, on any subject he thought convenient. Yet it was a circumstance of decency which Paul and Barnabas would hardly omit, to acquaint the rulers with their desire of doing it: probably by some message before the service began.