One of the beautiful things about Scripture is that the Author doesn't leave us hopeless. He balances hard truths such as those in the previous verses with passages filled with encouragement and purpose.
In this passage, Paul highlights the "how" of the Thessalonians' salvation:
- The sanctifying work of the Holy Spirit
- Belief in the truth
- through the proclamation of the Gospel
They were saved not by a mere set of facts, nor by any works of their own. Instead, God's men shared God's message, and the Thessalonians believed it. The Holy Spirit came into their hearts and began a transforming, sanctifying work. And that sanctifying work occurred as the believers held on to the word of God - the teachings passed on by the very apostles who brought the message to them. He charges them - and by extension, us - to stand firm - in contrast to those just mentioned in the previous verses who refused to love and believe the truth, delighted in wickedness, believed a lie, and were deceived by evil.
How do we stand firm? By holding to the teachings passed on by the apostles! Remember that Paul was writing this as one of the earliest books of the New Testament to be penned. The early church had the Septuagint (the Greek translation of the Old Testament), stories passed on by those who knew Jesus, and the few books that were written to this point. The "teachings passed on whether by word of mouth or by letter" incorporates all that was taught under the inspiration of the Holy Spirit. In John 17:20, Jesus extends His beautiful prayer beyond His immediate apostles to all those who would believe because of their words:
My prayer is not for them alone. I pray also for those who will believe in me through their message
In replacing Judas with Matthias in Acts 1, we learn that the criteria for apostleship was witnessing the resurrected Christ (Acts 1:21-22). Here is the apostolic authority laid out in Scripture: Those who were direct witnesses of the resurrected Christ recorded what He taught them, inspired by the Holy Spirit, and those writings became the New Testament. They became the "teachings passed on". They became the truths we are commanded to hold on to (and they point back to the Old Testament, reaffirming its role as authoritative in the church as well).
So Paul is telling the church in Thessalonica: "God called you through our words, saved you through your belief in the truth and through the indwelling Holy Spirit, and now teaches you through our words - so hold on to them. He's given you encouragement and hope that is eternal - beyond your circumstances. So just do and say what is right."
That's where the hope comes in! God gave us encouragement and hope, so that we can be encouraged and strengthened for doing and speaking what is right. But that hope isn't just a good feeling. It's not positive thinking. It's firmly rooted and grounded in the word of God. It looks a lot like this:
"I'm facing the temptation to compromise at work right now, by inflating my numbers. But God's Word tells me that God hates dishonest weights and measures, and tells me to be honest in all things. He tells me that He establishes the work of my hands. So I am going to trust Him and do what is right."
"Our finances are really tight, so we don't have extra money right now for anything. But that single mom in our church doesn't have enough money to buy food. Scripture tells us to always be ready to meet immediate needs and that we should always be ready to do good especially within the church. He also promises to provide for our needs. So we are going to trust Him and open our hands to her, by having a meatless week and giving the difference to help her with her financial needs."
The examples are endless but the principle is the same -- when faced with a specific situation, we find something in God's Word that speaks to that situation, and we believe what God says and act or speak accordingly.
We are given hope and eternal encouragement. But we won't find any of it apart from the Word of God. As Christians who want to stand firm, we must make Scripture central to our daily lives and to our churches. We must be sure that our belief in its accuracy and inerrancy is firmly grounded, then hold on to it (all of it) with all we have. It's the only way to stand firm.