Adam Clarke on 1 Thessalonians 3:6

When Timotheus came - We have already seen that he and Silas stayed behind at Thessalonica, when Paul was obliged to leave it; for the persecution seems to have been principally directed against him. When Paul came to Athens, he sent pressingly to him and Silas to come to him with all speed to that city. We are not informed that they did come, but it is most likely that they did, and that Paul sent Timothy back to Thessalonica to comfort and build up these new converts. After Paul had sent away Timothy, it is likely he went himself straight to Corinth, and there Timothy soon after met him, with the good news of the steadiness of the Thessalonian Church.

Your faith and charity - The good tidings which Timothy brought from Thessalonica consisted of three particulars:

1. Their faith; they continued steadfast in their belief of the Gospel.

2. Their charity; they loved one another, and lived in unity and harmony.

3. They were affectionately attached to the apostle; they had good remembrance of him, and desired earnestly to see him.