But the Comforter, the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you.

And when he is come, he will reprove the world of sin, and of righteousness, and of judgment.

Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you.

- St. John 16:7, 16:8, 14:26