Considering that (a) the apostle Paul was in Thessalonica for three Sabbath days (Acts 17:2), and (b) a good portion of the church was made up of former pagans (Acts 17:4, 1 Thessalonians 1:9), it is remarkable how much the apostle had to remind them of in his first letter (you can’t remind someone of something they don’t already know).
Click over to Y’Know, For the Thessalonians and read more about the “you know” refrain of 1 Thessalonians and its significance.