Here is an interesting verse that may open up our understanding a little better. 2 Thessalonians 2:15 NASB "(15) So then, brethren, stand firm and hold to the traditions which you were taught, whether by word of mouth or by letter from us." There was word of mouth teaching going on in the first century. That only makes sense, but think about how much of the teaching in your current church setting is word of mouth. Most right? Of-course! No matter how much your pastor or teacher sticks to the scripture, the bulk of every teaching is explanation that is word of mouth. Moreover, it is word of mouth based on the traditions and presuppositions that he or she has been taught. It is little wonder then that Paul would write about traditions that were taught by word of mouth as well as epistle. You can bet the farm that there was a lot more word of mouth than epistles.
Let's look a little deeper in the the passage in Paul's second epistle to the Thessalonians. 2 Thessalonians 2:13-15 NASB "(13) But we should always give thanks to God for you, brethren beloved by the Lord, because God has chosen you from the beginning for salvation through sanctification by the Spirit and faith in the truth. (14) It was for this He called you through our gospel, that you may gain the glory of our Lord Jesus Christ. (15) So then, brethren, stand firm and hold to the traditions which you were taught, whether by word of mouth or by letter from us." The letter/epistle explains it well, but let me unpack it a little... let me expand with what the actual word of mouth interpretation of the passage would be. So, we see first that they were chosen from the beginning for sanctification by the Spirit and faith in the gospel. Yes, when Paul writes faith in the truth, he is speaking of faith in the "word of truth" which he defined as the gospel in Ephesians 1:13. It is the gospel that allows one to gain the glory of the Lord Jesus Christ.
Well, how does it operate you ask? The gospel brings peace with Father God. It brings peace because one is accepted in Christ, completely forgiven, has been imputed the righteousness of Christ, God is no longer counting trespasses, but rather, has reconciled humanity to Himself through Christ. Paul said in Romans 5, "therefore, being justified by faith you have peace with God." Imagine that, having shalom with God. Peace with God is the foundation for transformation. The Holy Spirit uses the gospel message to create a sense of peace with God. That is the first and most important step in the transformation process.
Now then, follow on along this train of thought.... once a person believes the gospel by the power of the Holy Spirit, once one believes that they have peace with the Father based on Christ alone, at that moment, they begin to genuinely love God... How did John say it? Herein is love, not that we love God but that he loved us and sent His Son as a propitiation for our sin. The Holy Spirit uses the gospel message to give us peace with God and then as we believe the message, the Holy Spirit begins to generate within us a genuine love for God. Loving God for real.... not just saying so because we know it is a command, but because we believe the gospel. We believe that God was in Christ reconciling the world to Himself not counting sin. How can you not love God when you focus on that gospel truth? I'll bet right now as you read this, there is a feeling of warm peace welling up in your bosom, that is bringing about a transforming love for God.... You are witnessing the way in which the Holy Spirit transforms... you are experiencing it even as you read on. Yes, it is just this simple.
This is why the Law kills and the Spirit gives life! When you believe the gospel you are being transformed by the Holy Spirit. Unfortunately too many preachers think you need to hear the law so that the Holy Spirit can enable you to obey the Law. That is a lie from Satan and his minions! In order for the Holy Ghost to transform you by the gospel... you have to continually hear the gospel... is that what you hear most of the time in most churches? Absolutely NOT! Most of the time you hear the killing letter... you should be starting to see clearly. We'll stop for now and continue on later.