The moon is, by definition, secondary to the sun. The sun is the source of light, heat, and energy, the center around which the solar system revolves.
“The sun…is like a groom coming forth from his bridal chamber, rejoicing like a warrior to run the course. The end of the heavens is its source, and its circuit is to their other end; nothing is hidden from its heat.”
Those words are followed in Tehillim 19 by “The Torah of Hashem is trustworthy,” implying a connection between the constancy of the sun and the perfection of the Torah.
The moon, on the other hand, is the receiver, as opposed to the giver. Its glow comes from the sun.
The relationship between these two heavenly bodies is analogous to the relationship between Hashem and the universe He created. All life radiates from Him; we are receivers. He is like the sun and we are like the moon. He is constant and unwavering; we are unstable, in a constant internal and external battle for life. Sometimes we are strong and bright, sometimes weak and dark.
When the moon says that two kings cannot utilize the same crown, Hashem tells the moon, “diminish yourself!” Something similar happened when Chava rebelled against Hashem in Gan Eden. She was implicitly criticizing the way Hashem had set up the universe. This is like the moon telling Hashem that He set up the universe deficiently.
Both Chava and the moon suffered because they challenged Hashem. Chava was expelled from the constant goodness of paradise and the moon was expelled from receiving constant light and life from the sun. Hashem in His mercy continued to give Chava life, but not the eternal, stable life she had enjoyed in Gan Eden. So too, Hashem did not obliterate the moon or consign it to complete darkness, but diminished it until it retained its former full measure of light and life only on one day of the month.
On that day the moon returns to its former brightness and magnitude. On that day it shows “kavod” to the sun by not trying to encroach on its territory. On that day it receives the sun’s full blessing. So too with mankind: when we give Hashem His Place as the Master of the Universe, when we stop trying to encroach on His position by competing with Him, it is then that we enjoy His full blessing.
This is comparable to the proper respect accorded when a rosh yeshiva, a gadol, or, for that matter, a parent enters the room: we rise and remain standing until he is seated. This is “kavod h rav” or “kibud av v’eim.” We receive our life from the gadol and from our parents. We show our respect by standing and giving honor. Part of derech eretz is being able to accept that I am indebted to someone and accept his authority. When I acknowledge that, I am not lowering but rather elevating myself.
This is called “sameach b’chelko” – “being satisfied with one’s lot” (Pirkei Avos 4:1). We will never have menuchas hanefesh unless we can accept the portion Hashem gives us. The design of the entire universe is based on the allotments Hashem apportioned to each creation. If I try to grab someone else’s portion, I am going to throw the entire universe out of balance. The world is a mess today because we don’t understand this.
The Asseres haDibros end (Shemos 20:14) with “You shall not covet.” The source of trouble is our desire for that which does not belong to us, whether it is mankind desiring the fruit of a tree in Gan Eden, the moon envying the status of the sun, or any individual wanting something that belongs to someone else. The key to achieving peace in the world is the ability to accept what Hashem bestows upon us.