Apparently only shortly after writing his first letter to the Thessalonians, Paul had to write again to correct a false report that he had said the day of the Lord had already come. The day of the Lord was a phrase from the Hebrew prophets to describe God’s key victory over every opponent, when his faithful ones would be rewarded. The Thessalonians’ concern seems to have been not that the day had come and gone and they had missed it, but that it was now present. That would mean nothing more was to be expected from God in terms of setting things right. Since they continued to suffer persecutions, this was a depressing prospect.
Even before he contradicts this false report, Paul reassures the Thessalonians that God will indeed pay back all those who were troubling them. He reminds them of the details he had discussed with them in person of how the day of the Lord would arrive. He then repeats some instruction from his earlier letter, urging them not to be idle but to work hard and earn their own livings.
At the end of the letter, most of which would have been written by a scribe, Paul adds a greeting in his own handwriting. He wants them to know for sure this teaching is really coming from him!