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.” Ps. iv. 6. 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.” Eph. i. 13.