Prove, Hold Fast. 1st Thessalonians 5:21 Prophecies in this passage of scripture refer to the “forth-telling” of a message from God through a preacher. We need to understand that God uses others to minister to us, and we are not to despise what they know to be true. We may have never considered what they teach, but we can be edified, exhorted, and comforted when we "try the spirits" or test the teaching with the scriptures. The Bible is how God has chosen to communicate verbal truth so we can know and do His will. There is an unfortunate tendency to dismiss what someone else says when it doesn't agree with my opinion about a matter or an interpretation of a scriptural passage.
The Lord Jesus Christ warned His disciples about those who would teach false doctrine, and the apostles and prophets did the same after He ascended into heaven. These early gifted men were chosen by God to be the foundation on which we are built. We are responsible for accepting what is true, holding it firmly, and also for rejecting what is false because of its evil and the harm it causes.
When examining a teaching for reality, we can determine what is right or wrong. It is up to us to verify and prove what is correct. That should be our goal, not just to show that the other person is wrong. "The word of God is not bound." It is up to us to allow it to teach, guide, and empower us as we let the Spirit of God work through others for our benefit.
After evaluating what is said and verifying it by applying the word of God to the preacher's words, we need to personally and publicly hold fast to it, appreciate it, apply it, and use it appropriately to guide and strengthen our faith. Believers are called to be holy and live holy lives. That means we avoid what we know is evil and practice what we know is good. Holiness depends not only on what we don’t do because we are children of God but also on what we do according to the Lord’s will and commands.