Paul first visited Thessalonica round about 50 A.D., as described in chapter 17 of the book of Acts. He started by going into the synagogue, and he taught there on Saturdays for three weeks in a row. But then some opponents stirred up a mob against them, and they seized and beat up some of the believers including Jason, at whose house Paul had been staying. The opponents were motivated by jealousy, because they could see that a number of people were listening to Paul’s message.
At night time Paul was sent off to Berea. The opponents followed him there, so Paul had to leave and go to Athens. After spending some time there he moved on to Corinth, and the present letter to the Thessalonians appears to have been written from Corinth. In chapter 3 he said:
“[We] sent Timothy, our brother and God’s servant in the Good News of Christ, to sustain you and encourage you in your faith, so that no one would be discouraged by these persecutions. You know that these things will happen to us, because when we were with you, we told you in advance that we would suffer persecution.”
The recipients of the letter had become followers of Jesus even though Paul had only spoken with them for a short period of time, so they must have only had a basic understanding of what it meant to be a Christian. Even more remarkably they had held on to their belief with no external support or further teaching, in the face of continued persecution from Paul’s opponents. Something had given them the courage to persevere and endure persecution only three weeks after hearing about Jesus for the first time.