Apringius of Beja — on Rev 1:4 (TRACTATE ON THE APOCALYPSE 1:4)

“Here is that mystery of the number seven which is everywhere indicated. Here the seven spirits are introduced, which are one and the same Spirit, that is, the Holy Spirit, who is one in name, sevenfold in power, invisible and incorporeal, and whose form is impossible to comprehend. The great Isaiah revealed the number of its sevenfold powers when he wrote: "the Spirit of wisdom and understanding"—that through understanding and wisdom he might teach that he is the creator of all things—"the Spirit of counsel and might"—who conceived these things that he might create them—"the Spirit of knowledge and piety"—who governs the creation with piety by the exercise of his knowledge and whose purposes are always according to mercy—"the Spirit of the fear of the Lord"—by whose gift the fear of the Lord is manifested to rational creatures. This is itself the sacred character of the Spirit who is to be worshiped. It includes rather the ineffable praise, and does not indicate any form of nature.”