He calls Him not the Holy Spirit, but the Spirit of truth, to shew the perfect faith that was due to Him. He knew that He proceedeth from the Father, for He knew all things; He knew where He Himself came from, as He says of Himself above, I know whence I came, and whither I go. (John 8:14)
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Hom. lxxvii. 3