1 Thessalonians 4-5, 2 Thessalonians 1-3
2 Thessalonians 3:17
17 I, Paul, write this greeting in my own hand, which is the distinguishing mark in all my letters. This is how I write.
This seems like a trivial point, but why does Paul put this line in his letter? He’s writing to a group of people that know him well and have received a letter from him already.
My theory is that there were bogus letters circulating around the churches, and Paul is attempting to stamp them out.