In verse 28 he said, "Let them speak my word faithfully." It is so important that anyone who is a minister of the gospel presents God's Word in all truth and honestly. So many lives depend on what they tell them. Someone's life may be totally devastated if what is told them is false.
God will judge all who claim to be from Him just like He did the prophets of old. A lot of people today are looking for preachers that will tell them what they want to hear. Some have taken on a particular lifestyle and they need to hear someone say that it is alright to continue doing what they are doing. They don't care if it is right or not. The Bible states in 2 Timothy 4:3...For the time will come when they will not endure sound doctrine, but after their own lusts shall they heap to themselves, teachers, having itching ears.
But if you claim to be a servant of God and you claim to preach His word, make sure it is what would glorify God. When you speak, make sure it is God's Word and not your own.