9.

As for the sound of the voice, however, and the bodily form of a dove, and the cloven tongues which sat upon each of them, these, like the terrible wonders wrought at Sinai, ¹ and like the pillar of cloud by day and of fire by night, ² were produced only as symbols, and vanished when this purpose had been served. The thing which we must especially guard against in connection with them is, lest any one should believe that the nature of God--whether of the Father, or of the Son, or of the Holy Spirit--is susceptible of change or transformation. And we must not be disturbed by the fact that the sign sometimes receives the name of the thing signified, as when the Holy Spirit is said to have descended in a bodily form as a dove and abode upon Him; for in like manner the smitten rock is called Christ, ³ because it was a symbol of Christ.