Paul continues instructing the Thessalonians in how to conduct themselves when they come together to worship the Lord. And he encourages them with the wonderful truth that God is working in and through them to sanctify them. Their growth in holiness is sure for God is faithful.
The character of the Church must be patterned after the life and teaching of Christ and the character of any given church is shaped by conduct of her people. In these verses Paul provides instruction as to how God’s people should relate to one another with a specific emphasis on what are often some of the most challenging: Our relationships with those in authority and our relationships with those who require us to dig a little deeper to love well. Through Paul's instruction we will see that each one of us has an opportunity to contribute significantly to the Christlike character of the church.
In their exchange of letters, the Thessalonians ask the Apostle Paul the question we all want an answer to, when will the Lord return? Paul teaches them that the Day of the Lord will come unexpectedly and that for Christians, our focus needs to be on making ourselves ready for his appearing, not on dates. He further encourages them that they need not fear the Day of the Lord. For some it will lead to judgment, but for them, it will lead to their full salvation and even greater union with Christ.