AND THEY SHALL BE FOR LIGHTS IN THE FIRMAMENT OF THE HEAVEN TO GIVE LIGHT UPON THE EARTH. God added here that their light should reach the earth since it is possible for the light to be seen in the heavens and perform all mentioned functions without lighting upon the earth. Hence God said that it be for lights in the firmament of the heaven, directed toward the earth and shining upon it.
ברקיע השמים להאיר על הארץ, ”in the sky of the heavens to disseminate light all over the earth.” One of the luminaries’ functions is similar to that of lanterns which are also always placed on high poles to better illuminate their surroundings. According to the plain meaning of the text, the sun and moon are necessary to illuminate earth, whereas the light created on the first “day,” is needed to illuminate the heavenly regions, seeing that on the second “day,” a partition had been erected between the former and the latter by the horizon/atmosphere. Alternately, when the Torah reported that on the first “day” light came into existence, i.e. ויהי אור, this was the “light” which enabled “life” to exist, whereas here we speak about the light provided by the sun and moon respectively. Although as yet this “light” was not needed as the creatures for which the sun and moon were to shine had not been created yet, there were grasses and fruit bearing trees which needed it in order for them not to wither and die. The fruit could not have ripened without the rays of the sun. We also know from Deuteronomy 33,14, that there are plants which cannot grow without moonlight. Furthermore, G-d had created some living creatures such as creeping things and birds on the fifth “day,” and the means for their survival had to exist before they came into existence.
§ Rabbi Shimon ben Pazi raises a contradiction between two verses. It is written: “And God made the two great lights” (Genesis 1:16), and it is also written in the same verse: “The greater light to rule the day, and the lesser light to rule the night,” indicating that only one was great. Rabbi Shimon ben Pazi explains: When God first created the sun and the moon, they were equally bright. Then, the moon said before the Holy One, Blessed be God: Sovereign of the Universe, is it possible for two kings to serve with one crown? One of us must be subservient to the other. God therefore said to her, i.e., the moon: If so, go and diminish yourself.