Translated by Bl. Jackson.
80 Pages (Homilies: 1, 2, 3, 4, 5, 6, 7, 8, 9)
2. "And God said, Let there be lights in the firmament of the heaven to give light upon the earth, and to divide the day from the night."  Heaven and earth were the first; after them was created light; the day had been distinguished from the night, then had appeared the firmament and the dry element. The water had been gathered into the reservoir assigned to it, the earth displayed its productions, it had caused many kinds of herbs to germinate and it was adorned with all kinds of plants. However, the sun and the moon did not yet exist, in order that those who live in ignorance of God may not consider the sun as the origin and the father of light, or as the maker of all that grows out of the earth.  That is why there was a fourth day, and then God said: "Let there be lights in the firmament of the heaven."
When once you have learnt Who spoke, think immediately of the hearer. God said, "Let there be lights...and God made two great lights." Who spoke? and Who made? Do you not see a double person? Everywhere, in mystic language, history is sown with the dogmas of theology.
The motive follows which caused the lights to be created. It was to illuminate the earth. Already light was created; why therefore say that the sun was created to give light? And, first, do not laugh at the strangeness of this expression. We do not follow your nicety about words, and we trouble ourselves but little to give them a harmonious turn. Our writers do not amuse themselves by polishing their periods, and everywhere we prefer clearness of words to sonorous expressions. See then if by this expression "to light up," the sacred writer sufficiently made his thought understood. He has put "to give light"  instead of "illumination."  Now there is nothing here contradictory to what has been said of light. Then the actual nature of light was produced: now the sun's body is constructed to be a vehicle for that original light. A lamp is not fire. Fire has the property of illuminating, and we have invented the lamp to light us in darkness. In the same way, the luminous bodies have been fashioned as a vehicle for that pure, clear, and immaterial light. The Apostle speaks to us of certain lights which shine in the world  without being confounded with the true light of the world, the possession of which made the saints luminaries of the souls which they instructed and drew from the darkness of ignorance. This is why the Creator of all things, made the sun in addition to that glorious light, and placed it shining in the heavens.
 Gen. i. 14, LXX.
 Fialon quotes Bossuet (5th elev. 3d week): "Ainsi il a fait la lumiere avant que de faire les grands luminaires ou il a voulu la ramasser: et il a fait la distinction des jours avant que d'avoir cree les astres dont il s'est servi pour les regler parfaitement: et le soir et le matin ont ete distingues, avant que leur distinction et la division parfaite du jour et de la nuit fut bien marquee; et les arbres, et les arbustes, et les herbes ont germe sur la terre par ordre de Dieu, avant qu'il eut fait le soleil, qui devait etre le pere de toutes ces plantes; et il a detache expres les effets d'avec leurs causes naturelles, pour montrer que naturellement tout ne tient qu'a lui seul, et ne depend que de sa seule volonte."
 phausis, the act of giving light, LXX.
 photismos, the condition produced by phausis.
 cf. Phil. ii. 15.
Reference address : https://www.elpenor.org/basil/hexaemeron.asp?pg=49