The apostle has already given the reasons for "always giving thanks to God" for the Thessalonian believers (1:2). Now he has "another reason "(2:13), which causes his gratitude to God for this church.
They received the message of the apostle as being the actual word of God. Not merely as an "opinion", "judgement" or "religion" of the preacher, but as of divine origin, and so of undeniable authority. So they obeyed, putting into practice his commandments: faith in Christ as the Son of God and only and powerful Saviour - with the resulting holiness of life.
Note: The Bible clearly and consistently insists on its absolute authority as the Word of God, inspired by the Holy Spirit. "All Scripture is inspired by God and profitable for teaching, for reproof, for instruction in righteousness" (2 Timothy 3:16), "Knowing this, that no prophecy came by human will, but men spoke from God, moved by the Holy Spirit" (2 Peter 1:20-21). We also have the testimony of Jesus Himself: "The Scriptures ... are they which testify of Me" (John 5:39), "if you believed Moses, you would believe Me, for he wrote about Me. But if you do not believe his writings, how will you believe My words?" (John 5:46-47), "Your fathers ate the manna in the wilderness" (John 6:49), "The Scripture can not be broken" (John 10:35), see also Matthew 24:15 - "The prophet Daniel" and Luke 24:27, "beginning at Moses and all the Prophets, He expounded to them the things concerning Himself in all the Scriptures."
Such obedience to the Word of God brought to the Thessalonian believers harsh persecution by the Jews (see Acts 17:5), just as had happened in Judea in the early years of the Gospel. See Acts 4:15-18, 5:17-18, 5:30-33, 40-41, 6:8-14, 54-60.
Paul condemns the Jews very sternly. Not only did they kill the prophets but also their own Messiah and Saviour, and persecuted Paul and the other apostles (as we see in the book of Acts, from chapter 4 through to 25). They were fulfilling the parable in Mark 12:1-2, as well as the words of the Lord Jesus in Matthew 23:13. For their relentless persecution of the believers, the Jews were heaping sin upon sin, "filling the measure of their iniquity" (Genesis 15:16), see also Matthew 23:31-32.
Paul saw himself as "orphaned" - that is, separate and deprived from the presence of the Thessalonian Christians (see 2 Corinthians 11:28). He longed to visit them again, but the enemy constantly prevented him. How? Through diseases? Lack of funds for the journey? ... We do not know. Satan is always the adversary of God and of His people, making as difficult as possible the evangelical work and the witness of the believers. Paul writes elsewhere: "Put on the whole armour of God, that you may be able to stand against the wiles of the devil, for we do not wrestle against flesh and blood, but against ... spiritual hosts of wickedness, in the heavenly places." (Ephesians 6:11-12). The Apostle Peter writes: "Be sober, be vigilant; because your adversary the devil walks about like a roaring lion, seeking whom he may devour: Resist him steadfast in the faith ... " (1 Peter 5:8-9) .
"Our hope, or joy, or crown of rejoicing"- Paul looked forward to the arrival of the Lord, rejoicing in the souls that he would present to Christ as a result of his work, especially the believers in Thessalonica! (V.19). “Is it not you?" - is very emphatic, as seen in v. 20.
How deep was the love of Paul for his children in the faith!
13 For this reason we also thank God without ceasing, because when you received the word of God which you heard from us, you welcomed it not as the word of men, but as it is in truth, the word of God, which also effectively works in you who believe.
14 For you, brethren, became imitators of the churches of God which are in Judea in Christ Jesus. For you also suffered the same things from your own countrymen, just as they did from the Judeans,
15 who killed both the Lord Jesus and their own prophets, and have persecuted us; and they do not please God and are contrary to all men,
16 forbidding us to speak to the Gentiles that they may be saved, so as always to fill up the measure of their sins; but wrath has come upon them to the uttermost.
17 But we, brethren, having been taken away from you for a short time in presence, not in heart, endeavored more eagerly to see your face with great desire.
18 Therefore we wanted to come to you—even I, Paul, time and again—but Satan hindered us.
19 For what is our hope, or joy, or crown of rejoicing? Is it not even you in the presence of our Lord Jesus Christ at His coming?
20 For you are our glory and joy.
1 Thessalonians chapter 2, verses 13 to 20