When the Spirit of truth comes, he will guide you into all the truth. He will not speak on his own; he will speak what he hears, and he will announce to you the things to come.
In context
11and about judgment, because the ruler of this world already stands judged. 12I still have many things to tell you, but you cannot bear them now. 13When the Spirit of truth comes, he will guide you into all the truth. He will not speak on his own; he will speak what he hears, and he will announce to you the things to come. 14He will glorify me, because he will take what is mine and announce it to you. 15Everything the Father has is mine. That is why I said he takes what is mine and will announce it to you.