The Holy Spirit He calls the Comforter, a name taken from His office, which is not only to relieve the sorrows of the faithful, but to fill them with unspeakable joy. Everlasting gladness is in those hearts, in which the Spirit dwells. The Spirit, the Comforter, is sent by the Son, not as Angels, or Prophets, or Apostles, are sent, but as the Spirit must be sent which is of one nature with the Divine wisdom and power that sends Him. The Son when sent by the Father, is not separated from Him, but abides in the Father, and the Father in Him. In the same way the Holy Spirit is not sent by the Son, and proceedeth from the Father, in the sense of change of place. For as the Father’s nature, being incorporeal, is not local, so neither hath the Spirit of truth, Who is incorporeal also, and superior to all created things, a local nature.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Didym. De Spir. Sanct.