THE Father was the True Light which lighteneth every man coming into the world. The Son was the True Light which lighteneth every man coming into the world (Jn 1:9). The Other Comforter (Jn 14:16) was the True Light which lighteneth every man coming into the world.
Was and Was and Was, but Was One Thing. Light thrice repeated; but One Light and One God.
This was what David represented to himself long before when he said, In Thy Light shall we see Light (Ps 36:9). And now we have both seen and proclaim concisely and simply the doctrine of God the Trinity, comprehending out of Light (the Father), Light (the Son), in Light (the Holy Ghost).
He that rejects it, let him reject it; and he that doeth iniquity, let him do iniquity; we proclaim that which we have understood.
We will get us up into a high mountain (Is40:9), and will shout, if we be not heard, below; we will exalt the Spirit; we will not be afraid; or if we are afraid, it shall be of keeping silence, not of proclaiming.
St Gregory Nazianzen (329-389). The Fifth Theological Oration: On The Holy Spirit.
ALL-HOLY Spirit, that goeth forth from the Father and dwelt through the Son in unlettered disciples, Save and sanctify all them that acknowledge thee to be their God.
The Father is Light, the Word is Light, Light also is the holy Spirit, who was sent in fiery tongues upon the Apostles: through whom also all the world is led unto Light, to worship the holy Trinity.
Exaposteilarion at Orthros on the Feast of Pentecost.