The Holy Spirit.  Acts 1:4-8 And being assembled together with them, He commanded them not to depart from Jerusalem, but to wait for the Promise of the Father, “which,” He said, “you have heard from Me; for John truly baptized with water, but you shall be baptized with the Holy...

John 14:16-18 And I will pray the Father, and He will give you another Helper, that He may abide with you forever- the Spirit of truth, whom the world cannot receive, because it neither sees Him nor knows Him; but you know Him, for He dwells with you and will...