In the Blessing of the Moon (Birkat HaLevanah), we thank Hashem for creating the moon, and for the benefit we receive from its light. Many attach special honor to this blessing, because it alludes to deep concepts concerning the Jewish people. We will explain some of these ideas:
Of all the heavenly bodies, the moon is most similar to us. Just as a person’s life is filled with ups and downs, so too, the moon waxes and wanes. In the middle of the month, it looks full, but as it nears the end of the month it dwindles and disappears. And just as Adam paid dearly for giving in to his pride and desires when he ate from the Tree of Knowledge , so too, the moon was not satisfied with being originally the same size as the sun, wanting instead to rule over it (see above, sec. 5). In retribution for the moon’s arrogance, HaKadosh Baruch Hu reduced its light and created the lunar cycle in which its light decreases every month, eventually disappearing from the sky. However, unlike man, who fades away and dies, the moon is part of the heavenly hosts and is fixed and everlasting, always regenerating itself. The Jewish people have the exact same qualities. On the one hand, they lead normal human lives, which include ups and downs, with good inclinations as well as evil ones. Yet their connection to faith and God is everlasting. Therefore, unlike other nations, Am Yisrael endures forever. Thus we are reminded of Israel’s immortality in Birkat HaLevanah, when we see the moon reappear and grow stronger every month.
Moreover, not only do we manage to survive despite all the hardships, we actually advance to a higher level as a result of each crisis and setback. King David, whose kindom is compared to the moon, taught us how to transform each setback into an impetus for greater growth. Chazal tell us that David was the least esteemed of his brothers, growing up in the fields amongst the sheep, but he, matured and developed from every experience. Even after his difficult fall in the episode of Bat-Sheva, he didn’t give in to despair. Rather, he repented completely, to the point where Chazal say that “he established the yoke of repentance” (Mo’ed Kattan 16b). David transformed the regrettable incident into a catapult of tremendous self-improvement, setting an example for all generations. We learn from him the ways of repentance and its power of renewal. By virtue of his repentance, David’s kingdom is everlasting, just like the moon which always rejuvenates after its decline.
This is why we say in the Kiddush Levanah ceremony, “David, King of Israel, lives and endures.” Likewise, the Jewish people, as well, grow from every setback, rectifying all their sins and blemishes, until they will eventually be privileged to perfect the world through God’s sovereignty. At that time, the moon, which symbolizes our situation in the world, will also return to its perfected state, when its light will be as bright as the sun’s. Thus, we beseech God in Birkat HaLevanah, “It (the moon) should renew itself like a crown of glory for those borne from the womb (the people of Israel), who will eventually renew themselves like it and glorify their Maker for the sake of His glorious kingdom.”
Some have a custom to add the following request: “May it be Your will, Lord my God and God of my forefathers, to repair the moon’s defect, that there be no deficiency in it. Let the light of the moon be like the light of the sun and like the light of the seven days of Creation, as it was before it was reduced, as it says, ‘The two great luminaries’(Bereshit, 1:16). And may the following verse be fulfilled through us: ‘They shall seek the Lord their God and David their king’(Hoshea, 3:5). Amen.
 Numerous Midrashim indicate that the Gentiles follow the solar calendar, including the Christians. We can explain this as follows: The desire to utilize the sun stems from a desire for absolute perfection. However, that is beyond man’s reach. And since the Gentiles fail to attain absolute perfection, they forfeit what they could have achieved by revealing God’s Name in the world. The Jews, on the other hand, know how to operate within this world while clinging to God, which manifests itself through constant self-perfection. Calculating the months according to the moon’s cycle alludes to our efforts in this world, while calculating the years according to the sun’s orbit hints to our constant aspiration for perfection. The Muslims learned from the Jews to count by the moon, but only by the moon. This signifies a lack of aspiration for continuous self-perfection and an entrenchment in this world. It also explains why they perceive reward, even in the hereafter, in physical terms.
It is important to add that even when the moon is invisible to us, it remains whole in its “hiding-place.” It’s just that all the light it absorbs from the sun is reflected back towards the sun and is thus indiscernible on earth. The same is true of the Jewish nation: even when it descends, its inner essence remains unblemished, as it says, “You are entirely beautiful, my love, and there is no blemish in you” (Shir HaShirim 4:7).