20 But you have been anointed by the Holy One, and you all have knowledge. 21 I write to you, not because you do not know the truth, but because you know it, and because no lie is of the truth. 22 Who is the liar but he who denies that Jesus is the Christ? This is the antichrist, he who denies the Father and the Son. 23 No one who denies the Son has the Father. Whoever confesses the Son has the Father also.
24 Let what you heard from the beginning abide in you. If what you heard from the beginning abides in you, then you too will abide in the Son and in the Father. 25 And this is the promise that he made to us—eternal life.
26 I write these things to you about those who are trying to deceive you. 27 But the anointing that you received from him abides in you, and you have no need that anyone should teach you. But as his anointing teaches you about everything, and is true, and is no lie—just as it has taught you, abide in him.
The Holy Spirit is given to all believers and leads them all into the truth. It isn't just for the church leaders or disciples to pass on to others in apostolic succession.
There is some teaching that Jesus' promise of the Holy Spirit leading into truth and bringing to remembrance all things that He taught was just for the disciples, but it's obviously not.
The believer can depend on the leading of the Holy Spirit to teach him.
Acts 15:8 And God, who knows the heart, bore witness by granting them the holy Spirit just as he did us. 9 He made no distinction between us and them, for by faith he purified their hearts.