Our lessons today are a sharp contrast of spiritual darkness and spiritual light. The Old Testament lesson (Judges 19 & 20) reveals what happens when God's people lose connection with their Savior God.
In contrast, the congregation in Thessalonica has experienced enough of the darkness of this world that their focus is on the day of Jesus' return. Their faith and love are increasing. Paul assures them that when Jesus comes back on the last day, those who have persecuted them will be judged and they will join in the Lord's glory. Thus our prayer: Even so, come quickly, Lord Jesus.
In 2 Thessalonians 2, Paul deals with a fear that the Thessalonians have - that somehow Jesus returned, and they missed it. His response is an assurance that "the man of lawlessness" must first be revealed. I've pasted the section below so I can add some notes of explanation.
The Man of Lawlessness
Concerning the coming of our Lord Jesus Christ and our being gathered to him, we ask you, brothers and sisters, 2 not to become easily unsettled or alarmed by the teaching allegedly from us—whether by a prophecy or by word of mouth or by letter—asserting that the day of the Lord has already come. 3 Don’t let anyone deceive you in any way, for that day will not come until the rebellion [the Greek word always refers to a spiritual rebellion - apostasy--false teaching about how we are saved] occurs and the man of lawlessness is revealed, the man doomed to destruction. 4 He will oppose and will exalt himself over everything that is called God or is worshiped, so that he sets himself up in God’s temple [Paul refers to the church as God's temple--this person will be a part of the visible church], proclaiming himself to be God.
5 Don’t you remember that when I was with you I used to tell you these things? 6 And now you know what is holding him back [Here something is holding him back, in the next verse someone. What and who holds back a spiritual rebellion? The truth and Christ, the truth personified, holds him back], so that he may be revealed at the proper time. 7 For the secret power of lawlessness is already at work [Paul was already dealing with the belief that a person can be saved by what he does, or that Jesus' death on the cross is not sufficient to save us]; but the one who now holds it back will continue to do so till he is taken out of the way. 8 And then the lawless one will be revealed, whom the Lord Jesus will overthrow with the breath of his mouth [overthrown by the Word coming from Jesus] and destroy by the splendor of his coming [the man of lawlessness will continue to the end of the world--an indication this is more than just one individual but an on-going office]. 9 The coming of the lawless one will be in accordance with how Satan works. He will use all sorts of displays of power through signs and wonders that serve the lie [a warning that the devil can do supernatural things too. Don't be deceived], and all the ways that wickedness deceives those who are perishing. They perish because they refused to love the truth and so be saved. 11 For this reason God sends them a powerful delusion [an example of where God punishes sin with sin--when people refuse to believe, God punishes them by allowing them to be misled] so that they will believe the lie 12 and so that all will be condemned who have not believed the truth but have delighted in wickedness.
[The lesson to learn from this warning of the man of lawlessness is how important it is for us to be students of God';s Word and submit our lives to that Word. When we humbly admit the danger of being misled, we appreciate the promises in the next verses--all three persons of the Trinity are active in our salvation.]
13 But we ought always to thank God for you, brothers and sisters loved by the Lord, because God chose you as firstfruits to be saved through the sanctifying work of the Spirit and through belief in the truth. 14 He called you to this through our gospel, that you might share in the glory of our Lord Jesus Christ.