The apostle's first entrance to Thessalonica is recorded in Acts 17, where, as the result of his Gospel ministry, a people are found gathered as a Church in the assurance of God's salvation, and to the hope of the return of His Son from heaven (1 Thess. 1: 9). In the midst of many trials and persecutions they were serving the living and true God, to Whom they had turned from idols, and the report of their faith had gone forth through all that region. But having been forced suddenly away from this newly-planted Church by the enmity and opposition of the Jews, he manifests a special concern for them, and as a true pastor his heart is much moved toward them. Timothy had been sent to comfort them concerning their faith (1 Thess. 3: 2), and to strengthen them against the wiles of the tempter who was seeking to alarm and seduce them from the truth. With little to help and much to test them, they seem to have fallen under the power of two misapprehensions of the truth as taught by the apostle, one concerning their brethren who had fallen asleep, and the other concerning themselves who were alive. The former is especially dealt with in the first Epistle, the latter in the second. The return of Timothy to the apostle, brought the intelligence of their fears regarding those who had fallen asleep, that they might miss the joys awaiting those who would be found alive and waiting at the coming of the Son from heaven. To remove this anxiety and to impart a fuller revelation on the subject, the apostle writes to inform them that all the saints, whether sleeping or alive, would share the triumph of that day, and be caught up together to meet the Lord in the air (2 Thess. 4: 13-18), and to be with Him where He is.
The Second Epistle was drawn from him to remove another anxiety which had arisen among them touching the living saints, either from an imperfect, understanding of his first Epistle or from false suggestions or misrepresentations made by others. They feared that the saints living on earth when the "day of the Lord" was present would be involved in its judgments which the Scriptures inform us will characterise that period. To this the second Epistle makes reply by telling them that the day of the Lord could not come until the "man of sin" is revealed and the full apostasy from the truth is manifested (2 Thess. 2: 1-10). The distinction between the coming of the Son of God to the air with a shout for His people, to bring all, dead and living, of this heavenly household to His Father's house, and His return with them "in flaming fire" (2 Thess. 1: 7), as Son of Man and Minister of God's righteous wrath upon the world of the ungodly. These are the main subjects of these precious Epistles, with much to quicken faith and sustain hope while God's long-suffering lingers and the Gospel goes forth, bringing into the garner its sheaves for the heavenly harvest, with solemn warnings to saints as to watchfulness and walk, while the already working leaven of the coming apostasy is all around them.
