John 16:12-15 ESV
“I still have many things to say to you, but you cannot bear them now.
When the Spirit of truth comes, he will guide you into all the truth, for he will not speak on his own authority, but whatever he hears he will speak, and he will declare to you the things that are to come.
He will glorify me, for he will take what is mine and declare it to you.
All that the Father has is mine; therefore I said that he will take what is mine and declare it to you.
Jesus did not say all that He wanted to say because they would not be able to understand. They were not capable of understanding for they had not yet received the Holy Spirit. It takes the Spirit to guide us into the truth of God. His Spirit is able to declare the word of God to our spirit. Jesus spoke words our ears could hear. The Spirit speaks the word to our spirits. The word spoken is the same word, the word of God.