“If you love Me, keep My commandments. 16 And I will pray the Father, and He will give you another Helper, that He may abide with you forever— 17 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 be in you. 18 I will not leave you orphans; I will come to you.” — John 14:15-18.
Jesus expands on the wonder of God being three Persons in the Godhead by talking about the Holy Spirit. He tells His disciples that they would express their love for Him by keeping His commandments. Jesus would pray to the Father to give them another Helper — the Spirit of truth who dwells with them and would be in them — to help and abide for ever with them. He promises not to leave them orphans but come to them.