Now our Lord Jesus Christ himself, and God our Father, who loved us and gave us eternal comfort and good hope through grace,
In continuing this prayer, Paul prays that the Thessalonians, through grace, would have good hope, that is, that they would be "joyful and confident (in expecting) eternal salvation" (Thayer 205-2-1680). Since receiving the false or misunderstood teachings about the return of Christ, it seems they had doubts of their eternal home. With such doubts, they could not live in comfort. This good hope was made possible by the resurrection of Jesus Christ.