1 Thessalonians provides us with two verses (2:13 and 5:27) that help us explore the word of God, whether spoken or written.
The Spoken Word of God
“And we also thank God constantly for this, that when you received the word of God, which you heard from us, you accepted it not as the word of men but as what it really is, the word of God, which is at work in you believers” (1 Thess 2:13 ESV).
In this verse, Paul twice calls the content of his verbal witness to the Thessalonians “the word of God.” Though Paul spoke verbally, he spoke the word of God—this word’s origin was divine.
As to the verbal and unwritten nature of his witness to “the word of God,” it was “heard” by the Thessalonians. Luke variously describes Paul’s verbal witness to the Thessalonians as reasoning (dialegomai), explaining (dianoigō), proving (paratithēmi), proclaiming (katangellō), and saying (legō; Acts 17:2–3, 7). In hearing the word of God, the Thessalonians did not merely receive (paralambanō) it into their ears, but they also savingly accepted (dechomai) it for what it was—the very word of God.
So what exactly were these words that Paul called the word of God?
Looking again at Acts 17, the word of God included several truths: Jesus is the Christ, the promised Messiah; the Christ had to suffer and rise from the dead, events that perfectly matched the life of Jesus; the Old Testament Scriptures prophesied these events in detail; and Jesus is a King who is alive today (Acts 17:2–3, 7). And Paul certainly said much more in his first three weeks and time to come (cf. Acts 17:2). He gives us more details in 1 Thessalonians when he recounts what his readers believed: that idols are dead and false; that God is living and true; that God raised Jesus from the dead; that Jesus is God’s Son; and that Jesus will deliver us from the wrath to come (1 Thess 1:9–10). More than just merely acknowledging the content of truth, the Thessalonians embraced it in spite of persecution and knew the saving joy of the Holy Spirit, living by His power (1 Thess 1:6–7). They wholeheartedly rejected their former beliefs and way of life to turn to God and live for Him.
But still, should Paul definitively call his own verbal words the word of God?
As an apostle, Paul revealed part of the foundational truth necessary for the establishment of the church (Eph 2:20). In fact, Jesus revealed all of the truth necessary for this age through Paul and the other apostles (Eph 3:5; cf. John 16:13). The apostles verbally spoke these things at first, but as the church grew beyond their reach, they wrote letters, some of which were Scripture (more on this below). But until these letters were written, Paul and the other apostles could apparently say by the Spirit that their verbal witness was the very word of God. Apostles were not perfect and could even sin from time to time (e.g., Gal 2:14), but, based on Paul’s statement in 1 Thess 2:13, we could say that Paul perfectly spoke the very word of God in the exercise of his apostolic office. Much as the prophets of old could claim, “Thus saith the Lord,” so also the apostles spoke the word of God in their verbal, apostolic witness.
The Written Word of God
“I put you under oath before the Lord to have this letter read to all the brothers” (1 Thess 5:27 ESV).
Paul put the Thessalonians under an oath before the Lord Jesus Christ to read his letter before the assembly. Paul likely addressed the elders of the church and commanded them to read his letter before their brothers.
Paul’s command to publicly read this letter implied that this letter was Scripture (cf. 1 Tim 4:13). By binding his readers with an oath before the Lord Jesus indicated that Paul spoke on behalf of Christ. Thus, Jesus Himself commanded them to read this letter in the assembly. Though written by Paul, this was Christ’s word to the Thessalonians and is still His word to us today.
Paul certainly wrote other letters to edify the churches, letters that were not Scripture (e.g., 1 Cor 5:9; Col 4:16b). What makes 1 Thessalonians (or any other book of the Bible) Scripture is that the Spirit carried the author along in the writing process (2 Pet 1:20–21), producing Scripture, the written and inspired word of God, that which makes one wise to salvation and is profitable to equip him for every good work (2 Tim 3:15–17). Like other Scripture, God has providentially preserved the truth of 1 Thessalonians over time because of its necessary instruction (2 Tim 4:2; cf. 1 Tim 3:15), ongoing authority (John 10:35), and promised permanence (Matt 24:35). Paul consciously knew what words were from the Spirit through him to others, and thus he could forcefully bind his readers to an oath before the Lord to read his letter. Others recognized his letters as Scripture as well (2 Pet 3:15–16).
While we may not have the originals for this letter or the other biblical books, the promise of preservation implies that we have the written word of God today in the totality of its extant manuscripts. The best translations of Scripture are formally equivalent to the Hebrew, Aramaic, and Greek, providing a dynamic translation only when the meaning of the original text would be otherwise obscured.
Can We Speak or Write the Word of God Today?
As we have seen, in the exercise of their apostolic office, Paul and the other apostles could perfectly verbalize the word of God to others as Christ revealed foundational truth through them for the establishment of His church. Something foundational happens but once, and given the historically-conditioned requirements for apostles (cf. Acts 1:22–26; e.g., seeing Christ during the ministry of John the Baptist), we have no more foundational figures today (either apostles or prophets; Eph 2:20; 3:5). We can verbally preach and teach the written word of God, even accurately so (cf. 2 Tim 2:15), but this is different from perfectly orating the very word of God as the apostles did long ago.
As to writing the word of God, again, the apostles (and others) gave us the foundation and tradition in the Bible that we teach today. And as their role was qualified by history, so also was the New Testament era of writing God’s word. We can reflect something of God’s written words in writing (e.g., a biblical commentary), but this is infinitely different from revealing new words from God in written form today. Ever since the apostle John penned the “Amen” of Rev 22:21, no one has written new words from God for us today.