He is the Holy Spirit, who leads into all truth. The world cannot receive him, because it isn’t looking for him and doesn’t recognize him. But you know him, because he lives with you now and later will be in you. John 14:17

“When the Spirit of truth comes, He will guide you into all truth, for He will not speak on His own, but He will speak what He hears, and He will declare to you what is to come. He will glorify me because it is from me that he will receive what he will make known to you. He was speaking about the Spirit, whom those who believed in Him were later to receive. For the Spirit had not yet been given, because Jesus had not yet been glorified.”