The passage
      v1. The Thessalonians were unsure of what happens at the coming of Christ to believers who had already died. Paul answers this concern in 4:13-18. As for the actual date of Christ's return, Paul feels that he doesn't need to say much on this issue as he has already instructed them fully. They know all about the "times" and the "seasons".
      v2. Paul underlines the fact that the Thessalonians have a full understanding about the return of Jesus. Paul doesn't need to give them further instruction. They know that the Lord will return, and that his return will be when least expected. He uses the Old Testament term "day of the Lord" to describe the event. This is the language of the prophet Amos, Am.5:18ff. Whereas Israel saw this day as a day of judgement upon the nations, it is in fact a judgement which begins with God's people, so be warned!
      v3. "When 'all is well' and 'all is safe' are on the lips of men", Moffatt. The false prophets of Israel claimed that "all is well" just before the destruction of Jerusalem. We are reminded that judgement "begins with the house of the Lord"; those who claim to follow Christ will be the ones tested and tried. The coming disaster is described as "destruction". Its coming is inevitable, as is birth for a woman in labor. The meaning of "destruction" is "banishment from the living presence of the Lord", Morris, cf. 2Thess.1:9.
      v4. Paul now moves into a "be what you are" type of exhortation. His argument is simple, if we are children of light, rather than children of darkness, then let us live in a way that images what we will be in that coming day (in fact, what we are already in Christ). Paul affirms that the Thessalonians are children of light and will therefore not be surprised at the coming day.
      v5. The lives of the Thessalonian believers can be characterized as "light", "sons of the day." This description evidences their standing in the coming day, an inheritance which shapes them.
      v6. Paul therefore calls on his readers to live as children who are awake rather than "asleep" - asleep in the sense of insensitive to righteousness. They must be "alert and self-controlled", in "a state untouched by any slumberous or beclouding influences", Grimm-Thayer. Paul is calling on his readers to be wary of evil influences.
      v7. "Sleep", that is, moral indifference, is the business of darkness, of night. By implication, this is not the behavior of those who are "awake" and who walk in the light of the coming day.
      v8. So, as children of the "day, let us.....". Paul calls for soberness, in the sense of "self-control". He calls for the great Christian qualities of faith, hope and love. We are to put them on as if pieces of armor. Put them on decisively as defensive armor against "sleep". The "hope" is for salvation - the ultimate consummation of all things.
      v9. For those who believe, God's intention is not that they suffer his anger in the last day, but that they possess salvation (eternal life and all that this entails) and that they possess it in and through Christ. God's "wrath" displays his holiness, his reaction to evil.
      v10. Paul goes on to outline the basis of salvation, namely, the atonement - Christ's sacrificial death on the cross. The consequence of Christ's work for us is that whether we are "awake" (here means alive, "walking in life", Moffatt) or "asleep" (here means dead, "sleeping in death", Moffatt), we remain in an eternal relationship with Christ - "in Christ." Even in death we are still with Jesus. We may not be aware of this state, as we are unaware of our being with Jesus now, but in the day of resurrection we will certainly be aware of our standing in Christ.
      v11. Paul concludes with two exhortations. The first is "encourage one another" - "go on cheering and strengthening each other with thoughts like these", Phillips; "strengthen each other with truth." The second imperative is "build each other up." Paul likes this phrase and uses it of being built up, strengthened, grown spiritually, .... and this through Spirit-inspired truth. The teaching of Biblical truth promotes spiritual growth.

Building the people of God
      In the face of very powerful management and marketing methodologies, the church is increasingly tempted to turn toward secular systems for survival and growth. Yet, Christ's "kingdom is not of this world". Christ uses another methodology to strengthen his people and build his church; it is the teaching of Biblical truth.
      The church of Christ stands eternally secure in his presence. We are saved through his death and resurrection. Although we "belong to the day", the light of eternity, we live in the present. Living as "sons of the light" comes by the encouragement of eternal truth, of Biblical truth, taught and proclaimed by ministers of the word and inspired and empowered by the Holy Spirit.
      Our task is the hear this truth, believe it and pray for it to be realized in our lives and in the lives of our brothers and sisters in Christ.

v2
      akribwV adv. "very well" - accurately, precisely. Not a common word in Paul's usage and so possibly it was used in the letter from the Thessalonians. They know the details of the second coming, namely that Jesus will return unexpectedly and that's the end of the matter. The only people caught out will be those who don't believe in an unexpected return. "Perfectly well", NEB.
      kuriou (oV) "Lord" - Used initially of God in the LXX and then of Jesus in the New Testament. The phrase "day of the Lord" comes originally from Amos 5:18 and refers to the day of judgment. The loss of the article indicates it is now a technical term.
      nukti (nux, nuktoV) "night" - This image from Jesus is further developed by Paul in this passage. The early Christians came to believe that Jesus would return in the night, even Easter eve (Jerome). Paul develops the image of night in the terms of moral indifference and this was also used to identify a particular time for the return of Christ - a time of moral decay. Yet, the image is portraying a moment when we least expect it.

v3
      oJtan + subj. "while" - when. Forming an indefinite temporal clause. "When people are talking of how peaceful and secure life is", Barclay.
      eirhnh (h) "peace" - possibly in the sense of security, inward peace.
      asfaleia (a) "safety" - secure from outward threat. cf Ezk.13:10. The false prophets proclaimed security and safety when there was none.
      aifnidioV adj. "suddenly" - Either sudden destruction as an adjective, or suddenly /all of a sudden, if used as an adverb.
      oleqroV (oV) "destruction" - disaster, ruin. This word is opposite to salvation/life and therefore illustrates disaster in the sense of separation from God. "Suddenly they will suffer terribly", TH.
      wdin (in inoV) "labor pains" - Often used to describe God's judgment in the Old Testament. The idea is not describing inevitability, but rather suddenness.
      ekfugwsin (ekfugw) aor. subj. "escape". "Escape there is none", Moffatt.

v4
      skotei (oV) "darkness" - Here the sense is of the realm of wickedness.
      katalabh/ (katalambanw) aor. "should surprise" - should overtake, take. Different meanings are possible, such as "harm" or "seize", but "surprise" seems best.
      klepthV "thief" - The end will come just as suddenly and unexpectedly for the believer, but we will not be surprised as a thief is surprised by the light of the new day.

v5
      uJioi fwtoV "sons of light" - In the sense of belonging to Christ the light. "Sons" is idiomatic, so "you belong to the light", CEV.
      uJioi hJmeraV "sons of the day" - In the sense of belonging to the age to come, the new day.

v6
      kaqeudwmen (kaqeudw) subj. "let us .... asleep" - let us [not] sleep. Hortatory subjunctive. The image is of moral laxity.
      grhgorwmen (gregorew) subj. "alert" - let us keep awake, be vigilant, watchful. Here of moral alertness and vigilance against evil.
      nhfwmen (nhfw) subj. "self-controlled" - sober, not influenced by alcohol. The idea is either of self-control, or quietness of mind, both of which are lacking in an intoxicated person.

v7
      oiJ mequskomenoi (mequskomai) pas. part. "those who get drunk" - the ones being drunk. The participle as a substantive. The sober sleep at night while the drunkard parties at night. The sons of the day / light sleep at night. "Drunkards", Moffatt.

v8
      de "but" - but, and. Here adversative.
      onteV (eimi) pres. part. "since" - The participle of the verb "to be" is adverbial, causal.
      hJmeraV (a) gen. "[we] belong to the day" - of day. The genitive is possessive, as NIV.
      hnfwmen (nhfw) pres. subj. "let us be self-controlled" - may be sober. Hortatory subjunctive.
      endusamenoi (enduw) aor. part. "putting on" - having clothed/armed oneself with. The participle is modal, expressing the manner of being self-controlled. "It is not enough to watch and be sober, we must also be armed", Chrysostom.
      qwraka pistewV kai agapaV "[putting on] faith and love as a breastplate" - put on faith and love as we would arm ourselves with a breastplate. In Ephesians 6:10-18 Paul uses a similar image of the Christian soldier's armor. In Ephesians the breastplate is "righteousness." Paul's meaning is open to debate. Is he telling us to take on the divine qualities of Christ through identification with Christ (possible imagery from Isaiah), or is he telling us to behave in a particular way (righteousness then means acting rightly)? If Paul is developing an ethical idea here, then it is the putting on of love and faithfulness (rather than faith in Christ), in the sense of doing it.
      perikefalaian elpida sowhriaV "the hope of salvation as a helmet" - We must put on the hope of salvation as we would arm ourselves with a helmet. Here the imagery is the same as Ephesians, and as in Ephesians, it is difficult to see how the imagery is ethical in nature. On the surface it seems like an exhortation toward assurance - "be sure of your eternal hope, your salvation."

v9
      ouk eqeto (tiqhmi) aor. "did not appoint" - did not put. The word "appoint" carries with it divine intent in the sense of "chose", "destined", but a simple sense of the word is probably intended, so "put". God did not gather us into the Christian fellowship to then destroy us.
      orghn (h) "wrath" - wrath / anger. In v9-10 Paul defines the basis of our assurance, but here he takes a negative tack. We are not set to face condemnation in the day of judgment.
      peripoihsin (iV ewV) "receive" - obtain, acquire. Here the positive, the gift of eternal life.
      dia + gen. "through" - through, by means of. Paul then states the means of our salvation, "through", in the sense of the causal activity of Christ. Here his death.

v10
      tou apoqanontoV (apoqnhskw) aor. part. "he died" - the one having died. Participle as a substantive. Paul defines the causal activity of Christ in his death on our behalf.
      iJna + subj. "so that" - in order that [...... we might live]. Forming a purpose clause.
      aJma sun "together with" - most agree that the words should be separated. "We might together live with him."
      zhswmen (zaw) aor. subj. "we may live" - The purpose of Christ's death on our behalf is that we might live eternally with him. Possibly hortatory, "we should live together with him", Moffatt.
      kaqeudwmen (kaqeudw) subj. "asleep" - we are sleeping. Here the sleep is most likely the sleep of death, while those who are awake are those who are living now. Paul does seem to have changed the imagery at this point from the imagery of waking and sleeping earlier in the passage. A bit confusing!