Most of the New Testament Epistles conclude with a benediction wherein the author expresses his wish for his audience and calls on God to bless them (e.g., Rom. 15:33; Eph. 6:23–24; Heb. 13:20–21). First Thessalonians likewise features a benediction from Paul at the end of the letter, as we see in today’s passage (1 Thess. 5:23–24).
The Apostle gives us a prayer, but there is much we can learn about God and how He works from these words. First, Paul calls for “the God of peace himself” to “sanctify you completely” (v. 23).The Apostle has called for peace to rule the Thessalonians (vv. 3, 13), but this prayer reminds us that any true peace finds its origin in the Creator. If we are to be at peace with one another, the Lord must grant it to us. This is confirmed in Paul’s prayer that God would sanctify his audience. Although we are called to act in the process of sanctification, to obey the Lord and make use of the means of grace (the Word, sacraments, prayer) as we work out our salvation (Phil. 2:12–13), we do not make ourselves holy. Instead, our Father sanctifies us. He transforms us by His Holy Spirit as we seek to follow His Son. Sanctification means not that we attain holiness solely through our own efforts but that God works in and through us to conform us to Christ (2 Cor. 3:17–18).
Moreover, Paul wants the Lord to sanctify his readers “completely” and make our whole “spirit and soul and body” blameless at the return of Christ (1 Thess. 5:23). Some interpreters have said that this verse reveals a tripartite division of human nature into body, soul, and spirit, a view known as trichotomy. However, we should not press Paul’s language in this way. The full scope of Scripture supports dichotomy (the doctrine that human beings have two constituent parts: body and soul/spirit), and even Paul speaks only of body and soul/spirit in other places (Matt. 10:28; 1 Cor. 7:34). Paul refers to body, soul, and spirit to stress the sanctification of every aspect of human beings. God will make everything about us holy.
Paul has no doubt that God will answer his prayer and sanctify the Thessalonians because he knows that the Lord is faithful to His promises to renew His children (1 Thess. 5:24). John Calvin comments, “When the Lord has once adopted us as his sons, we may expect that his grace will continue to be exercised towards us.”