Paul claimed that the Thessalonians received the Gospel in the power of the Spirit (1Thessalonians 1:5). In other words, the word of God so worked in their hearts, that they were moved to believe the Gospel (1Thessalonians 2:13). In so doing, they had come to recognize Paul and those who were with him as men sent to them by the Lord, just as the prophets of old had been sent to the people by the Lord. Nevertheless, unlike the people to whom the prophets were sent (Isaiah 53:1), the elect at Thessalonica not only believed Paul, but imitated him and preached the Gospel to others, as well (1Thessalonians 2:5-6).
Luke describes Paul’s entry into Thessalonica as coming to the synagogue and worshiping there. One thing led to another, until a dispute developed between Paul and the Jewish authorities in the synagogue, and for three weeks they debated over the authenticity of the Gospel. Out of that debate, a portion of the Jews and the God-fearing gentiles were called out of the assembly by the Spirit, in that they believed Paul and Silas (Acts 17:1-4).
Although Luke tells us that Paul’s debate with the Jewish authorities lasted three weeks (Acts 17:2), this doesn’t necessarily mean Paul was in Thessalonica for only three weeks. We are told Paul set up his own business in the marketplace of the city to support himself and his party, while they ministered in the city. In so doing, he wouldn’t have to beg for support from the new believers (1Thessalonians 2:9; 2Thessalonians 3:8). This might indicate that he was there for a longer period of time. His dispute with the elders of the synagogue may have been the climax of Paul’s ministry there. If he had been successfully convincing Jews that Jesus was the Messiah, the debate (1Thessalonians 1:2) may have been the result of that success. In other words, because Paul’s telling of the Gospel was so successful, the Jewish authorities challenged Paul, and that challenge took three weeks before it erupted into persecution and expulsion from the city.
If Paul’s reasoning came from the Scriptures (Acts 17:2), what may have been the argument the Jewish leaders presented to counter Paul’s point that Jesus was the Messiah? I believe we may get a hint of what that could have been from Acts 17:11. There we are told that the Bereans were more noble than the synagogue leaders at Thessalonica, in that the Bereans not only received what Paul claimed with a readiness of mind, but they searched the Scriptures to prove whether or not Paul was correct. On the face, this tells us that the leading Jews at Thessalonica didn’t dispute with Paul out of the Scriptures. Yet, Paul’s argument that Jesus is the Christ did come from them. So, whatever their dispute with Paul may have looked like (cp. John 12:34), it seems probable to me that they neither received Paul’s testimony with readiness of mind, nor did they dispute with him out of the Scriptures. In other words, the Jewish authorities probably argued against Paul by claiming what he said contradicted the tradition of the elders (cp. Matthew 15:2; Mark 7:3, 5; 23:30-31; Luke 6:22-23). The problem is that tradition contradicted the Scriptures and made the word of God of no effect among the Jewish congregation (Matthew 15:6; Mark 7:13).
The end result of the dispute between Paul and the elders at Thessalonica was that not only many Jews believed, but the greater part of the gentile God-fearers who worshiped with the Jews in the synagogue believed as well (Acts 17:2-4). Luke mentions that the elders of the synagogue “were moved with envy” (G2206), which may indicate that they sought to “zealously affect” (same Greek word; cp. Galatians 4:17) both the Jews and gentiles who believed Paul, first by shunning them, and then, through fear, by claiming Paul and company preached against the decrees of Caesar and had caused trouble throughout the Empire (Acts 17:5-9).
The point of the argument against Paul and company was that he preached that Jesus was the Messiah, the ruler of the world, which might have been construed to go against the decree of Tiberius Caesar, who made it unlawful to prophesy against any leader in the Empire, claiming there would be a change of leadership due to ill health or some such thing,[1] which Jews were known to do.[2] Moreover, at this time (cir. 50-51 AD) there had been several messianic figures who arose in Jerusalem, which the procurators there had either slain or captured. Moreover, there had also been a disturbance at Rome over one Chrestus (Christ / Messiah), and Claudius Caesar expelled all Jews from Rome to quiet the disorderly behavior (cp. Acts 18:1-2).[3] Thus, great efforts were made by the unbelieving Jewish authorities to accuse Paul falsely of wrong doing, for certainly he was not a disciple of any of the then current messianic figures rising up in Jerusalem; nor was he predicting the death or advocating the overthrow of any current political figure. However, if the unbelieving Jews could make their charges stick, Paul would have been in serious trouble, and all these things were known by those who had received the Gospel through Paul’s preaching (cp. 1Thessalonians 1:5).
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[1] This decree was made cir. 16 AD after the death of Caesar Augustus. See Dio Chrysostom 57.15.8 cp. Dio Cassius 56.25.5-6
[2] See Josephus: Antiquities of the Jews 17.2.4. There certain Pharisees had predicted the death of Herod at the time of the birth of Jesus.
[3] See Suetonius, Life of Claudius, 25.