John 16:13-15
13 But when He, the Spirit of truth, comes, He will guide you into all the truth; for He will not speak on His own, but whatever He hears, He will speak; and He will disclose to you what is to come. 14 He will glorify Me, for He will take from Mine and will disclose it to you. 15 All things that the Father has are Mine; this is why I said that He takes from Mine and will disclose it to you.
Here the Lord assures his apostles that failing memory will not be a problem for them in their role as witnesses to what they saw, what they heard and what they witness. Jesus will send the Spirit of Truth to help these men remember what Jesus spoke and what he did. He tells them that the Spirit of truth will not speak on his own but "whatever he hears." The Spirit of Truth will "take from mine", meaning the teaching of Jesus and his miracles and disclose it to the apostles. Jesus declares that the Spirit of Truth will guide the Apostles in what ever "he hears", taking from Jesus the knowledge and wisdom given to him and disclosing it to his apostles. In this manner, the spirit of Truth will glorify Jesus.
This supports my contention that the only two people authorized to tell us what to believe is Jesus Christ and God the Father. The Spirit of Truth is revealing what he hears from God the Father and the Lord Jesus Christ.