Paul commends the Thessalonians church because they "received the word of God." This is a very important point that Paul is making. The church did not declare the scriptures and Paul did not declare the scriptures. He is an apostle, but even an apostle has to submit to the scripture. So we see what the Belgic Confession is teaching us that scripture testifies to its own authority, and the Holy Spirit also continually bears witness to the word of God.