Each Person of the Trinity is said in the sacred writings to be Light. The Spirit is designated Fire by Isaiah, a figure of which Fire was seen in the bush by Moses, in the tongues of fire, and in Gideon's pitchers. And the Godhead of the same Spirit cannot be denied, since His operation is the same as that of the Father and of the Son, and He is also called the light and fire of the Lord's countenance.
160. But why should I argue that as the Father is light, so, too, the Son is light, and the Holy Spirit is light? Which certainly pertains to the power of God. For God is Light, as John said: |For God is Light, and in Him is no darkness.|
161. But the Son, too, is Light, because |the Life was the Light of men.| And the Evangelist, that he might show that he was speaking of the Son of God, says of John the Baptist: |He was not light, but [was sent] to be a witness of the Light. That was the true Light, which lighteth every man that cometh into this world.| So, then, since God is Light, and the Son of God the true Light, without doubt the Son of God is true God.
162. And you find elsewhere that the Son of God is Light: |The people that sat in darkness and in the shadow of death have seen a great light.| But, which is still more clear, it is said: |For with Thee is the fount of Life, and in Thy light we shall see light,| which means that with Thee, O God the Father Almighty, Who art the Fount of Life, in Thy Son Who is the Light, we shall see the light of the Holy Spirit. As the Lord Himself shows, saying: |Receive ye the Holy Spirit,| and elsewhere: |Virtue went out from Him.|
163. But who can doubt that the Father is Light, when we read of His Son that He is the Brightness of eternal Light? For of Whom but of the Father is the Son the Brightness, Who both is always with the Father, and always shines, not with unlike but with the same radiance.
164. And Isaiah shows that the Holy Spirit is not only Light but also Fire, saying: |And the light of Israel shall be for a fire.| So the prophets called Him a burning Fire, because in those three points we see more intensely the majesty of the Godhead; since to sanctify is of the Godhead, to illuminate is the property of fire and light, and the Godhead is wont to be pointed out or seen in the appearance of fire: |For our God is a consuming Fire,| as Moses said.
165. For he himself saw the fire in the bush, and had heard God when the voice from the flame of fire came to him saying: |I am the God of Abraham, and the God of Isaac, and the God of Jacob.| The voice came from the fire, and the voice was in the bush, and the fire did no harm. For the bush was burning but was not consumed, because in that mystery the Lord was showing that He would come to illuminate the thorns of our body, and not to consume those who were in misery, but to alleviate their misery; Who would baptize with the Holy Spirit and with fire, that He might give grace and destroy sin. So in the symbol of fire God keeps His intention.
166. In the Acts of the Apostles, also, when the Holy Spirit had descended upon the faithful, the appearance of fire was seen, for you read thus: |And suddenly there was a sound from heaven, as though the Spirit were borne with great vehemence, and it filled all the house where they were sitting, and there appeared unto them cloven tongues like as of fire.|
167. For the same reason was it that when Gideon was about to overcome the Midianites, he commanded three hundred men to take pitchers, and to hold lighted torches inside the pitchers, and trumpets in their right hands. Our predecessors have preserved the explanation received from the apostles, that the pitchers are our bodies, fashioned of clay, which know not fear if they burn with the fervour of the grace of the Spirit, and bear witness to the passion of the Lord Jesus with a loud confession of the Voice.
168. Who, then, can doubt of the Godhead of the Holy Spirit, since where the grace of the Spirit is, there the manifestation of the Godhead appears. By which evidence we infer not a diversity but the unity of the divine power. For how can there be a severance of power, where the effect of the working in all is one?
169. What, then, is that fire? Not certainly one made up of common twigs, or roaring with the burning of the reeds of the woods, but that fire which improves good deeds like gold, and consumes sins like stubble. This is undoubtedly the Holy Spirit, Who is called both the fire and light of the countenance of God; light as we said above: |The light of Thy countenance has been sealed upon us, O Lord.| What is, then, the light that is sealed, but that of the seal of the Spirit, believing in Whom, |ye were sealed,| he says, |with the Holy Spirit of promise.|
170. And as there is a light of the divine countenance, so, too, does fire shine forth from the countenance of God, for it is written: |A fire shall burn in His sight.| For the grace of the day of judgment shines beforehand, that forgiveness may follow to reward the service of the saints. O the great fulness of the Scriptures, which no one can comprehend with human genius! O greatest proof of the Divine Unity! For how many things are pointed out in these two verses!