Author — Paul.
Date — Written from Corinth circa A.D. 51 (a few months after 1 Thessalonians).
Purpose — To clear up confusion about second coming of Christ.
1:1 [cf. 1 Thess. 1:1] Paul [head of the missionary team that had brought Gospel to Thessalonica], Silas [also called Silvanus; called a prophet in Acts 15:32] and Timothy [cf. Acts 16:1-3], To the church [Gr. ekklesia: an assembly] of the Thessalonians [capital and largest city of Roman province of Macedonia] in God our Father and the Lord Jesus Christ:
1:2 Grace [God’s unmerited favor bestowed upon sinful people] and peace [made possible by Christ who is our peace (Eph. 2:14)] to you from [introduces source of “grace and peace”] God the Father [reminds us that we are part of a larger family of faith] and the Lord [our Master; deserves our obedience] Jesus Christ [Gr. form of “Messiah”].
1:3 We ought [implies personal obligation] always to thank God for you, brothers, and rightly so [fitting or appropriate in the circumstances], because your faith is growing [Gr. hyperauxenei: flourishing (like a healthy plant); our faith should grow as we mature in Christ; Thessalonians’ faith grew as a result of facing persecution and trials] more and more [growth beyond what is expected], and the love [Gr. agape] every one of you has for each other is increasing [Gr. pleonazei: spreading out or dispersing quickly (like floodwaters); cf. 1 Thess. 3:12].
Note: “…faith is a relationship of trust in God, and like all relationships is a living, dynamic, growing thing.” (John Stott)
1:4 Therefore, among God’s churches we boast [for the purpose of providing an example to other churches and challenging other churches to raise their level of commitment] about your perseverance [bearing up under difficult circumstances] and faith in all the persecutions [pressure, tribulation inflicted by the enemies of the gospel; suffering for religious convictions; cf. 1 Thess. 2:14] and trials [general word for difficulties, burdens, pressures in life] you are [indicates their sufferings were present realities] enduring.
Note: Do you think people tend to grow more in times of testing or in times of calm?
1:5 All this [growing faith, increasing love, perseverance in persecution (cf. 1:3-4)] is evidence [proof; plain indication] that God’s judgment [God’s decision to allow His people to suffer (in order to sanctify them)] is right, and as a result you will be counted worthy [their endurance indicated their faith was genuine] of the kingdom of God, for which [for the sake of which] you are [at the present time] suffering.
Note: Persecution and suffering are unavoidable for Christ’s followers. Read John 15:20-21; Acts 14:22; Romans 8:17.
1:6 God is just [His very nature is justice (cf. Deut. 32:4; 2 Chron. 19:7)]: He will [certainty; in His own time] pay back [to recompense; to give what is rightly deserved] trouble [pay back in kind] to those who trouble [to put someone under pressure; to persecute] you
Note: How can dwelling on our troubles cripple our faith?
1:7 and give relief [rest; release tension (as a bow string); perhaps relief that sufferings resulted in growth or that one day God will deal with those who persecuted them] to you who are troubled, and to us as well. This [relief] will happen when the Lord Jesus is revealed [Gr. apokalypsis: unveiling] from heaven in blazing fire [fire may refer to presence of the Lord or to judgment] with his powerful angels.
1:8 He will punish [cf. Deut. 32:35] those who do not [because of willful rejection, not innocent ignorance] know God and do not obey the gospel of our Lord Jesus.
1:9 They [such people] will be punished with everlasting destruction [refers to eternity in hell; destruction without end; does not mean annihilation; conscious and everlasting life of punishment] and shut out from the presence of the Lord [the worst aspect of hell is separation from presence of God, who is the Source of life] and from the majesty of his power
1:10 on the day he comes to be glorified in his holy people [designates “all those who have believed”] and to be marveled at among all those who have believed. This includes you, because you believed our testimony to you.
1:11 With this in mind [to this end], we constantly pray for you [we should pray for fellow believers],  that our God may count you worthy [prayer for the sanctification of believers] of his calling [that we become like Christ (cf. Rom. 8:29; 1 Jn. 3:2)], and  that by his power he may fulfill every good purpose of yours and every act prompted by your faith.
1:12 We pray this so that the name of our Lord Jesus may be glorified [to say things to enhance the reputation of Jesus; our goal ought to be to glorify Christ through every aspect of our lives] in you [we are to be instruments for His glory], and you in him, according to the grace of our God and the Lord Jesus Christ.