v1-11: Paul continues his teaching about the Lord's return, and application into our lives today.
v1: "Times and dates"; the time of the Lord's return, and the Day of the Lord, have not been revealed to man.
v2-3: "You know", as in 4.2,9; Paul reminds them of things he had previously taught them; perhaps these things had been neglected or forgotten. We must seek the mind of the Lord, and obey what He reveals.
The Day of the Lord is different to the Lord's return, although they are clearly related. The Lord's return is to gather His people. The Day of the Lord brings judgment upon unbelievers; it will come at a time when people do not expect it. The world will speak of peace and safety, but that will be a false security. Paul also refers to labour pains in Rom 8.22; this is something unexpected and serious; the unbelievers shall not escape the sudden destruction.
v4-5: True Christians need not fear the Day of the Lord. We are sons of the day and sons of the light, we must therefore live accordingly.
v6-8: Since we belong to the day, we must live godly; alert and self-controlled, putting on faith and love and hope.
v9-11: Our hope is in Christ. First, God has appointed us to salvation, and to be delivered from wrath (2 Thess 2.13). Second, there is the promise that we shall be with Christ together. Third, we can and must build each other up (4.18). Again, the truth of Christ’s return is a motivation to godly living.
v12-13: Proper respect for leaders in the church. We are commanded to esteem them very highly, and to avoid criticism. Some who laboured faithfully were not properly recognised as elders and deacons. Proper respect for leaders leads to peace in the church.
v14: People are individuals, and must be treated as such; some are idle, some timid, some weak, and we must treat them all with patience.
v15-18: Coping with our circumstances; we are to be joyful and prayerful and thankful. As in 4.3, where God’s will is that we be holy, so here God’s will for us is that we be joyful, prayerful, and grateful.
v19-20: Experiencing God is part of Christian life; we need the Spirit's fire, not just good words. And we need to hear God's voice, and obey it. It seems that some despised prophecies brought to strengthen the church. Some observe more ‘charismatic’ styles of church life, fear the excesses, and then reject the good. But God does speak to us, and does make Himself known to us, and we dare not neglect this.
v21: Test all things. In whatever age there are many voices, and many doctrines. We must test all things by the word of God.
v22: Avoid evil in every form, since it takes many forms. This is true within the church as outside.
v23: The aim of all things, that we might be fully set apart for God, and sanctified completely, Lev 20.7-8. This includes being blameless in body, 4.3-8; 1 Cor 6.15-19. Again, Christ's return motivates us to true holiness.
The person is spirit, soul, and body. Each is important, and each is to be holy to God. Since by nature we are corrupt in all things (as in Rom 3.10-18), so God will sanctify us completely.
v24: Our confidence is in God, who is working in us. He will bring us into conformity with Christ (Rom 8.29).
v25-28: Paul's final greetings; it was important that the letter be read to the whole church, that all might share, and all might learn.