Did you know that many of the Psalms are connected? They may have been written by the same author or refer to the same event. Psalms 3 and 4 are one such pair. Others are Psalms 1 and 2, 18 through 21, 42 and 42, and 118 and 119. Some psalm are theologically paired while others are companions that tell a story.
The two letters to the church at Thessalonica were an address to the local church and touch on issues that still apply to the church today: evangelism, ethics, fellowship, worship, obedience, hope. There is a message for pastors about serving their church with the gospel in the first letter.