But you have received the Holy Spirit, and he lives within you, so you don’t need anyone to teach you what is true. For the Spirit teaches you everything you need to know, and what he teaches is true–it is not a lie.
— I John 2:27 NLT
Preachers and teachers of the word of God and the gospel of Jesus Christ are sent out by God into the world. They proclaim the truth to those who have not heard the message. By God’s grace the Holy Spirit is given to some who hear the message and the Spirit enables them to believe that the message is true. Those who believe that it is true call upon the name of the LORD and are saved (Romans 10:13-15).
The Holy Spirit’s work in those who accept the message is not a one-time event. Rather, the Holy Spirit remains with them and lives within them permanently. As a result, they have the permanent ability to recognize what is true and not true when it comes to the word of God and the gospel of Jesus Christ. They do not need to be taught this. If any anti-Christian false prophets come their way, they have the ability to recognize that the message they preach is wrong.
However, the Apostle John is not saying that no Christian will ever need a teacher again. Since teaching is one of the gifts of the Holy Spirit (Romans 12:6-8), that interpretation doesn’t make much sense. What he is saying is that the Holy Spirit within us helps us to recognize what is true and not true when it comes to the word of God and the gospel of Jesus Christ. We don’t need another person, like a teacher, to take on this responsibility for us. Spirit-filled Christians that we are, we are capable of doing it for ourselves.
Although Godly teachers and preachers can help us develop and deepen our understanding of the truth and can help us develop and deepen our faith in the truth, we don’t need them to help us recognize truth. We don’t need to frantically search for reliable people to tell us what is true and what is not every time there is a question.
Given the indwelling presence of the Holy Spirit, we have what we need to keep from being fooled by the false prophets of the world.