St. Augustine: "The sending of the Holy Spirit"

“THIS operation, visibly exhibited, and presented to mortal eyes, is called the sending of the Holy Spirit; not that His very substance appeared, in which He Himself also is invisible and unchangeable, like the Father and the Son, but that the hearts of men, touched by things seen outwardly, might be turned from the manifestation in time of Him as coming to His hidden eternity as ever present.”

~St. Augustine: De Trinitate, 2, 5.

Pentecost, by Sir Anthony van Dyck. Oil on canvas, 1618-20; Staatliche Museen, Berlin.