14 And would you know that He discourses and speaks? Philip by revelation of an Angel went down to the way which leads to Gaza, when the Eunuch was coming; and the Spirit said to Philip, Go near, and join yourself to this chariot. Do you see the Spirit talking to one who hears Him? Ezekiel also speaks thus, The Spirit of the Lord came upon me, and said unto me, Thus says the Lord. And again, The Holy Ghost said , unto the Apostles who were in Antioch, Separate me now Barnabas and Saul for the work whereunto I have called them.
Beholdest thou the Spirit living, separating, calling, and with authority sending forth? Paul also said, Save that the Holy Ghost witnesses in every city, saying that bonds and afflictions await me. For this good Sanctifier of the Church, and her Helper, and Teacher, the Holy Ghost, the Comforter, of whom the Saviour said, He shall teach you all things (and He said not only, He shall teach, but also, He shall bring to your remembrance whatever I have said unto you; for the teachings of Christ and of the Holy Ghost are not different, but the same)— He, I say, testified before to Paul what things should befall him, that he might be the more stout-hearted, from knowing them beforehand.
Now I have spoken these things unto you because of the text, The words which I have spoken unto you, they are spirit; that you may understand this, not of the utterance of the lips, but of the good doctrine in this passage.
Source: Catechetical Lectures (New Advent)