John 16:12-14

“I still have many things to say to you, but you cannot bear them now. However, when He, the Spirit of truth, has come, He will guide you into all truth; for He will not speak on His own authority, but whatever He hears He will speak; and He will tell you things to come. He will glorify Me, for He will take of what is Mine and declare it to you.

1 Corinthians 14:2

For he who speaks in a tongue does not speak to men but to God, for no one understands him; however, in the spirit he speaks mysteries.