Chapter III.
To be the light of the day is one thing, to be the light of the stars is another. The difference between day and night is marked by two signs, and fire has a dual operation, to illuminate and to burn, which will be separated in the retribution of merits. God is said to be a consuming fire, and the reason why. Finally, every body clings to its own shadow.
Moreover, it can be moved, as it says: Let there be lights in the expanse of the heavens to separate the day from the night (Gen. 1:14). For also earlier, when he made the light, God had said, \"Let there be a separation among light and darkness.\" And there was evening, and there was morning, one day. But let us consider that the light of the day is different from the light of the sun and moon, and the light of the stars, because the sun itself seems to add its brightness to the daylight with its rays, which can reveal either the rising or the setting of the day. For before the sun shines indeed, but the day does not shine brightly; because it shines even more with the midday sun. This is shown by the Prophet, saying: And he will bring forth your justice as the light, and your judgment as the noonday (Ps. XXXVI, 6). For he compared the saint's justice not only to light, but also to the midday light.
9. Then he desired not only one sign, but also two, of daylight and of night: so that day might be made by the light's discrimination, and by the dawning of the sun; and again the failing of light and the uprising of stars might distinguish nightfall from day, and the beginning of night. For when the sun sets, yet somewhat of the day remains, until darkness cover the earth: and then follows the rising of the moon and the stars. And from the night indeed it is clear, that lunar and stellar illumination testifies to the spaces of night. Indeed, during the day that lunar radiance, and the rising sun, hide all the stars. Moreover, the sun itself can teach us about the different nature of daylight and the sun, and that it appears discolored. For the species of light is simple; it produces light. But indeed, the sun has not only the power to illuminate, but also to heat; for it is fiery. Fire both illuminates and burns. Therefore, the Lord, desiring to show Moses the miracle of His operation, by which He would provoke Moses to strive for obedience and inflame his desire for faith, appeared in fire in the bush, and the bush was not consumed, but only seemed to shine with the appearance of fire. Therefore, one duty was to be empty (vacabat) of burning, while the other was to be active (operabatur). The duty of burning involved the power of consuming, while the duty of illuminating involved the power of shining. That is why Moses was amazed, because the fire did not burn the bush against its nature, which typically burns even more flammable material. But the fire of the Lord is accustomed to illuminate, not to burn.
But perhaps you say: How is it written: I am a consuming fire (Deut., IV, 24)? You have rightly admonished. It does not usually consume, except sins alone. In the same way, the nature of fire is divided in terms of retributive merits; it illuminates some, it burns others. It illuminates the righteous, it burns the wicked. Those it illuminates, it does not burn; and those it burns, it illuminates. But its illumination is unquenchable for the completion of the good, its burning is intense for the punishment of sins.
11. But let us return to the cycle of day and night. With the rising light of day, night flees; with the setting of the day, night comes. There is no fellowship between light and darkness, for the Lord established this by natural law in His first work. Indeed, when He created light, He also created the distinction between light and darkness. In the course of the day itself, when the sun is already shining upon the earth, we see the shadow of a man or of a tree separate from the light, moving towards the West in the morning, turning back towards the East in the evening, and inclining towards the North during the midday hours. However, it does not confuse or mix with the light, but retreats and moves away. Similarly, night seems to give way to day, and to decline from its light; for, as more experienced people have demonstrated to us who have gone ahead of us in age or office, the shadow of the earth naturally clings to and attaches itself to the body, so much so that even painters endeavor to depict the shadows of the bodies they have painted, and they assert that it is a skill of art not to interrupt the force of nature; and it is as if someone who violates natural law, whose painting does not even express its own shadow. Therefore, just as during the day when a body comes into the path of the sun, from the side where the light is reflected, a shadow is cast, so when the day recedes and an object is encountered in the direction of its light or the sun, the air is shaded. Hence it is clear that shadows make night on the Earth.