Jesus was the herald of God. His authority was the authority of him who sent him. That same authority is held by every spokesman who speaks in accordance with the Bible. That is why a pastor says amen
at the end of his sermon. It is because he is convinced that he has spoken God’s word in all its purity. If he does not know that, he should not say amen.
It is true that ministers/pastors are not infallible. They can be wrong, even if they conclude their amen
with conviction. When that is the case, the pastor has to publicly correct that as well. He was speaking publicly, as the herald of God, and therefor he should also publicly correct himself and bring the truth.
17 From that time Jesus began to preach, saying, “Repent, for the kingdom of heaven is at hand.”