Basil of Caesarea

The first word of God created the nature of light; it made darkness vanish, dispelled gloom, illuminated the world, and gave to all beings at the same time a sweet and gracious aspect. The heavens, until then enveloped in darkness, appeared with that beauty which they still present to our eyes. The air was lighted up, or rather made the light circulate mixed with its substance, and, distributing its splendour rapidly in every direction, so dispersed itself to its extreme limits. Up it sprang to the very æther and heaven. …

The Hexaemeron, Homily 2: The Earth Was Invisible and Unfinished ↗

Cosmas Indicopleustes

God said, Let there be light, and the nature of fire came into being. And again proceeding He says: But our souls He fenced round with the body, while He made the angels bodiless. So then, what we see to be the case with respect to human souls and to angels, the same is the case with respect to fire, for the fire above subsists without matter, but the fire below with matter, for the fire above is akin to the fire below, just as our souls are also akin to the angels. How so? because the former are spirit and the latter too are spirit.

The Christian Topography, Book 10 ↗

Ambrose of Milan

God is the author of light, and the place and cause of darkness is the world. But the good Author uttered the word light so that he might reveal the world by infusing brightness therein and thus make its aspect beautiful. Suddenly then, the air became bright and darkness shrank in terror from the brilliance of the novel brightness.

The Six Days of Creation ↗

Bede

And God said, "Let there be light," and there was light. It is fitting for the works of God that the adornment of the world should begin with light: for since He Himself is the true light and dwells in inaccessible light, whose most blessed vision the angels in the heavens of heavens began to enjoy immediately after they were created, He also suitably granted to this world the first grace of material light to be its adornment, so that the other things He created might appear from the source of that light. …

Commentary on Genesis (Hexaemeron) ↗

Bonaventure

Now rightly the whole of time, which runs its course according to a threefold law, namely the law implanted within, the law given from without, and the law infused from above, runs through seven ages and is consummated at the end of the sixth; so that the course of the world may correspond to its origin, and the course of the greater world may correspond to the course of life of the lesser world, namely man, for whose sake it was made. …

Breviloquium, Prologue ↗