“Paul, and Silvanus, and Timotheus, unto the church of the Thessalonians in God our Father and the Lord Jesus Christ: Grace unto you, and peace, from God our Father and the Lord Jesus Christ” (2 Thessalonians 1:1-2).
This second letter to the church at Thessalonica was probably written within a few months of the first. This letter deals with the worsening problems the church was facing, especially those caused by false teachers who were still claiming that Christ had already returned. This brought further confusion to the believers, so Paul writes again to clear up important issues and destroy the foundation the false teachings were built upon.
The purpose of this letter
The same themes are dealt with in this letter as were found in the first, yet this is not repetition but reinforcement of the truth. To be reminded about vital truths is not a bad thing anyway, “Finally, my brethren, rejoice in the Lord. To write the same things to you, to me indeed is not grievous, but for you it is safe” (Philippians 3:1). The purpose of this second letter is threefold:  to encourage the church, who were still young in the faith and thus vulnerable to false teaching and temptation to give up because of persecution;  to exhort them to live holy and disciplined lives despite the difficulties they were undergoing;  to eradicate the false teachings regarding the last days.
The tone of Paul’s first letter is that of a tender nurse caring for the young, “But we were gentle among you, even as a nurse cherisheth her children” (1 Thessalonians 2:7), but here he is more like a father who is forced to discipline his wayward children.
God our Father
Paul uses almost the same greeting as in his first letter to Thessalonica, “Paul, and Silvanus, and Timotheus, unto the church of the Thessalonians which is in God the Father and in the Lord Jesus Christ: Grace be unto you, and peace, from God our Father, and the Lord Jesus Christ” (1 Thessalonians 1:1). The only difference is in that he uses “God our Father” rather than “God the Father.” Maybe he is emphasising that God is a personal God. By writing “our” he is inviting them to accept that they too belong to Him and are in no way less important to the Lord. They may have forgotten that he described God as such in his first letter. “To the end he may stablish your hearts unblameable in holiness before God, even our Father, at the coming of our Lord Jesus Christ with all his saints” (1 Thessalonians 3:11).
Also the use of “our Father” highlights the fact that God is our Father rather than simply being the Father of the Lord Jesus Christ. Once again this brings home to us the personal relationship we have with Almighty God. We have the privilege of calling Him “our Father” as expressed in the disciple’s prayer (Matthew 6:9-13). Only a true child of God can call God “Father”. This is why Paul encouraged believers to call God “Abba”. “For ye have not received the spirit of bondage again to fear; but ye have received the Spirit of adoption, whereby we cry, Abba, Father. The Spirit itself beareth witness with our spirit, that we are the children of God” (Romans 8:15-16) … “And because ye are sons, God hath sent forth the Spirit of his Son into your hearts, crying, Abba, Father” (Galatians 4:6). This was the title Jesus gave to His Father when He prayed, “And he said, Abba, Father, all things are possible unto thee; take away this cup from me: nevertheless not what I will, but what thou wilt” (Mark 14:36). Therefore, in light of these references, only someone who is “in” Christ can call God “Abba”. It is of some interest that the Aramaic word “Abba” means “O Father.” This is one of the signs that show repentant sinners are truly born again, and have the blessing to approach “God both with the confidence, and the tempers, of dutiful children” (John Wesley).
Though Paul’s greeting in his second letter is not dissimilar to the first, we can already see how he aims to deal with the issues that the Thessalonians were facing. It is a shorter epistle, yet it is just as powerful as anything the apostle wrote. We have this wealth of teaching in our hands, so we do well to get it into our hearts as Paul expected the Thessalonian believers to do.