Complete Works of Philo Judaeus, Vol. 1

These boundaries are "evening and morning," of which the former heralds the sun that is about to rise, gently restraining the darkness; while the evening comes upon the setting sun, softly receiving the sudden rush of darkness. And these, I mean morning and evening, must be placed in the order of the incorporeal and intelligible; for there is absolutely nothing sensible in them, but all are ideas, measures, types, and seals, which are incorporeal bodies for the creation of other bodies. And since light was created, darkness stood aside and retreated, and boundaries were fixed in the intermediate spaces—evening and morning—the measure of time was immediately completed, which the Creator also called "day." And he called it not "the first day," but "one day," which is so named because of the singularity of the intelligible world, which possesses a monadic nature.

§. 10. The incorporeal world, then, had already reached its end, established in the divine Logos Word/Reason, and the sensible world was being perfected after this as a model. And first of its parts, which is also the best of all, the Creator made the heaven, which he aptly named "firmament," as it is bodily; for a body is solid by nature, because it is extended in three dimensions. What other conception of a solid and a body is there, than that which is extended in every direction? Reasonably, therefore, contrasting the sensible and bodily to the intelligible and incorporeal, he called this the firmament. Then, he straightway and very appropriately called it "heaven," either because it was already the limit of all things, or because it was the first of the visible things to come into being. He also names the second day after its creation, assigning the whole interval and measure of a day to the heaven, due to its status and honor among sensible things.