II Thessalonians 2:1 Now concerning the coming of our Lord Jesus Christ and our being gathered together to him, we ask you, brothers, 2 not to be quickly shaken in mind or alarmed, either by a spirit or a spoken word, or a letter seeming to be from us, to the effect that the day of the Lord has come. 3 Let no one deceive you in any way. For that day will not come, unless the rebellion comes first, and the man of lawlessness is revealed, the son of destruction, 4 who opposes and exalts himself against every so-called god or object of worship, so that he takes his seat in the temple of God, proclaiming himself to be God.
Paul now turns his attention to the second coming of Christ, just as he had in his former letter. People get all excited when they think about this, and rightfully so. But the things we get excited about are also the things we can get fearful about. As followers of Christ, they had no need to fear. There would be "fair warning" to His coming, including an obvious imposter. After describing the deceiver's delusion, Paul goes on to remind them that they were saved, being sanctified and sealed by the Spirit of God. They were not to be shaken but stand firm and the faith and serve well until the Savior returns. The same is true of us.