Rabbi Zechariah said: After (the words) "the burnt offering of every month throughout the months of the year" (ibid.), what is written? "And one he-goat for a sin offering unto the Lord" (Num. 28:15). For what purpose was the sin offering? When the Holy One, blessed be He, created His world, He created two great luminaries, as it is said, "And God made the two great lights" (Gen. 1:16).
The one He made larger and the other smaller, and the moon obstinately refused to do the will of its Creator so as to be made smaller; therefore Israel offered on its behalf the he-goat for a sin offering heavenwards as one of the burnt offerings of the New Moon, as it is said, "And one he-goat for a sin offering unto the Lord" (Num. 28:15). What is the meaning of "unto the Lord"? The Holy One, blessed be He, said: This he-goat shall be an atonement for Me, because I have diminished the (size of the) moon.