At any moment, Paul has warned his listeners, an outpouring of divine wrath would engulf unsuspecting humanity and bring it sudden destruction (1 Thess. 1:10; 5:3; cf. 2 Thess. 1:5-10)...
Yet Paul had been entrusted by God to deliver to the Thessalonians a message of “good news” about “salvation” (2:4, 16; 5:9) – a salvation that, in light of humanity’s impending doom, was of a very specific sort. In Jesus, God’s Son, there is rescue from the coming wrath (1:10; 5:9). Paul does not [in 1 Thessalonians] spell out precisely how Jesus, or the gospel, effects salvation. It is clear, however, that the faith of believers included the conviction that Jesus had died and risen again (4:14). The Lord’s death, moreover, was “for us”... the death of Christ made it possible for those who believe to be “with him” (rather than objects of wrath) forever (5:10).
...Both acceptance and rejection of the truth are all-encompassing: life is either lived in the acknowledgment and service of the true and living God or in defiance of the truth. Those who reject the truth of the gospel act entirely in character when they do so: they are, in effect, refusing to abandon the life they have already adopted, in which neither acknowledging nor pleasing God plays a role (4:5; 5:7). Their unbelief is itself disobedience, and the disobedience shown in their actions is merely an expression of unbelief (cf. 2 Thess. 1:8; 2:10, 12). Conversely, those who respond in faith to the gospel are thereby turning away from a life of disobedience to one oriented around service to God (1 Thess. 1:8-9). Living in a way that pleases God is a natural and, in the end, inevitable expression of such faith: Paul rejoices when he sees the Thessalonians’ faith in action (1:3; 2 Thess. 1:11). That their faith remains deficient (1 Thess. 3:10) and has room to grow (3:2; cf. 2 Thess. 1:3) does not imply that they harbor doubts of the truth of their convictions; rather, there is still – and throughout their earthly lives there will be (cf. 1 Thess. 3:12-13; 4:1, 10: 5:23) – a need to express more consistently and completely the practical implications of their faith.
~ Stephen Westerholm, Perspectives Old and New on Paul