Ambrose of Milan — on 2Cor 3:6 (On the Holy Spirit, Book 2, Chapter 4.29-31)

“And what wonder is it the Spirit works Life, Who quickens as does the Father and as does the Son? And who can deny that quickening is the work of the Eternal Majesty? For it is written: "Quicken Thy servant." He, then, is quickened who is a servant, that is, man, who before had not life, but received the privilege of having it. Let us then see whether the Spirit is quickened, or Himself quickens. Now it is written: "The letter killeth, but the Spirit giveth life." So, then, the Spirit quickens. But that you may understand that the quickening of the Father, Son, and Holy Spirit is no separate work, read how there is a oneness of quickening also, since God Himself quickens through the Spirit, for Paul said: "He Who raised up Christ from the dead shall also quicken your mortal bodies because of His Spirit Who dwelleth in you."”