How do we know the authority of the apostles' teachings is true?

The authority of the apostles' teachings is rooted in their direct appointment by Jesus Christ and their inspiration by the Holy Spirit. As Jesus commissioned them in Matthew 28:19-20, He entrusted them with the Gospel message, commanding them to teach all nations. This authority is not based on their own merit but on the divine mandate they received. Furthermore, 2 Timothy 3:16-17 states that all Scripture is God-breathed and useful for teaching, showing that the words of the apostles carry the weight of divine inspiration, which is crucial for the foundation of faith in Christianity.