Paul and his friends worked and sacrificed to save people, but if they then fell away, that would have broken the hearts of the evangelists.
However, the Christians at Thessalonica remained faithful and even grew in spirit,
“But now that Timothy has come to us from you, and brought us good news of your faith and love, and that you always have good remembrance of us, greatly desiring to see us, as we also to see you—therefore, brethren, in all our affliction and distress we were comforted concerning you by your faith” (1 Thessalonians 3:6-7).
Therefore, even in the midst of persecution, Paul rejoiced because the Thessalonians remained in faith and love.
You do the same, and you will repay whoever led you to Jesus.