11 And these things perhaps should be otherwise explained; but now again we must hear the words of the Saviour Himself concerning the Holy Ghost. For He says, Unless a man be born of water and of the Spirit, he cannot enter into the kingdom of God. And that this grace is from the Father, He thus states, How much more shall your heavenly Father give the Holy Spirit to them that ask him. And that we ought to worship God in the Spirit, He shows thus, But the hour comes and now is, when the true worshippers shall worship the Father in Spirit and in truth; for the Father also seeks such to worship Him.
God is a Spirit; and they that worship Him must worship Him in spirit and in truth. And again, But if I by the Spirit of God cast out devils; and immediately afterwards, Therefore I say unto you, All manner of sin and blasphemy shall be forgiven unto men; but the blasphemy against the Holy Ghost shall not be forgiven. And whosoever shall speak a word against the Son of man, it shall be forgiven him; but whosoever shall speak a word against the Holy Ghost, it shall not be forgiven him, neither in this world, neither in the world to come. And again He says, And I will pray the Father, and He shall give you another Comforter, that He may be with you for ever, the Spirit of Truth; whom the world cannot receive, because it sees Him not, neither knows Him; but you know Him, for He abides with you, and shall be in you. And again He says, These things have I spoken unto you being yet present with you.
But the Comforter, which is the Holy Ghost, whom the Father will send in My name, He shall teach you all things, and bring to your remembrance all things that I said unto you. And again He says, But when the Comforter has come, whom I will send unto you from the Father, even the Spirit of Truth, which proceeds from the Father, He shall testify of Me. And again the Saviour says, For if I go not away, the Comforter will not come unto you..... And when He has come, He will convince the world of sin, of righteousness, and of judgment; and afterwards again, I have yet many things to say unto you, but you cannot bear them now.
Howbeit, when He the Spirit of Truth has come, He will declare unto you all the truth; for He shall not speak from Himself; but whatsoever He shall hear that shall He speak, and He shall announce unto you the things to come. He shall glorify Me, for He shall take of Mine, and shall announce it unto you. All things that the Father has are mine; therefore said I, That He shall take of Mine, and shall announce it unto you</em>. I have read to you now the utterances of the Only-begotten Himself, that you may not give heed to men's words.
Source: Catechetical Lectures (New Advent)