"Now when they had gone through Phrygia and the region of Galatia, they were forbidden by the Holy Spirit to preach the word in Asia. After they had come to Mysia, they tried to go into Bithynia, but the Spirit did not permit them. So passing by Mysia, they came down to Troas. And a vision appeared to Paul in the night. A man of Macedonia stood and pleaded with him, saying, 'Come over to Macedonia and help us.' Now after he had seen the vision, immediately we sought to go to Macedonia, concluding that the Lord had called us to preach the gospel to them" (Acts 16:6-10).
After working their way through Phyrgia and the region of Galatia, Paul, Silas, and Timothy are forbidden by the Holy Spirit to preach the gospel in the Roman province of Asia. Furthermore, the Spirit did not allow them to travel to Bithynia. So, instead they came to Troas. Luke does not explain how or why the Holy Spirit prohibited these men from evangelizing in certain areas. We are left to speculate that it may have had something to do with personal safety or divine timing. Perhaps it was not safe to travel in those regions at that time. Or, more likely, perhaps it was not the right time to preach the gospel there because there were souls ready to be harvested elsewhere. In either case, the prohibition was temporary. The gospel would eventually go to Asia and Bithynia.
While in Troas, Paul had a night vision. Its interpretation was clear enough. God wanted them to go to Macedonia to preach the gospel to the people there. As we will soon see, there was an evangelistic door of opportunity that God wanted them to take advantage of. Again, this may explain the earlier forbidding the Holy Spirit did. As a side note, it appears that Luke, who wrote the book of Acts, joins the group at Troas. This is evident from the sudden pronoun shift from "they" to "we," which would include the writer.
"Therefore, sailing from Troas, we ran a straight course to Samothrace, and the next day came to Neapolis, and from there to Philippi, which is the foremost city of that part of Macedonia, a colony. And we were staying in that city for some days. And on the Sabbath day we went out of the city to the riverside, where prayer was customarily made; and we sat down and spoke to the women who met there. Now a certain woman named Lydia heard us. She was a seller of purple from the city of Thyatira, who worshiped God. The Lord opened her heart to heed the things spoken by Paul. And when she and her household were baptized, she begged us, saying, 'If you have judged me to be faithful to the Lord, come to my house and stay.' So she persuaded us" (Acts 16:11-15).
After some more traveling, the evangelistic team eventually came to Philippi in Macedonia and stayed there many days. As was their tradition, they went on the Sabbath to where the religious-minded people gathered. In Philippi, it was a custom of some to offer prayer outside the city on the riverbank (there was no synagogue in Philippi). On this particular day there was a group of women gathered, and they gladly received the gospel message Paul preached. They had prayed to God and He had answered their call! He did not send an enlightening influence of the Holy Spirit upon their hearts, but He providential brought to them a preacher who could teach them the way of salvation.
One woman gathered there is mentioned by name: Lydia. The description of her indicates she was a business woman and sold items particularly to the wealthy. In that era, only the rich could afford purple garments. The purple dye was extremely hard to come by and thus expensive. More importantly, Lydia worshiped the true God and was receptive to the good news of Jesus Christ she learned that day! She had a good and honest heart that was opened by the Lord through the word of God Paul spoke, and she was willing to immediately obey the gospel after she heard it. Both Lydia and her household were baptized into Christ that day. Some have tried to make a case for infant baptism from this passage. They somehow "reason" that if she had a "household" then she must have had a young child or two. Friends, this simply doesn't follow logically! There is as much evidence in this passage for infant baptism as there is for baptizing one's household pet!
Lydia shows her gratitude and heart for hospitality as she pressures the evangelistic group to stay at her home (cf. Gal. 6:6). It appears they may have refused initially but eventually did stay with her.