“And God made the two great luminaries: the great luminary to rule the day and the small luminary to rule the night” (Bereishit 1:16). “Rabbi Shimon ben Pazi raised an apparent contradiction: the above verse first states “and God made the two great luminaries”, and the verse then states “the great luminary” and “the small luminary”?! The Moon said to God: “Master of the Universe, is it possible for two rulers to share one crown?” God said to the Moon: “Go and shrink yourself …” (Gemara Chulin 60b).
Rabbi Betzalel HaKohen MiVilna asks: Why did Rabbi Shimon ben Pazi insist on his interpretation that originally the Sun and Moon were both great luminaries but because the Moon complained it became a small luminary? Couldn’t he simply read the verse as “And God made the two great luminaries: the greater luminary to rule the day and the smaller luminary to rule the night”, i.e. that the Sun was always greater than the Moon? Maybe the luminaries are initially both called “great luminaries” because they are both “great” relative to the other heavenly bodies?
Gemara Yoma 62b teaches regarding the Yom Kippur offerings that when the Torah emphasises “And he should take the two goats” (VaYikra 16:5) it means that both goats must be exactly identical, in appearance, height and value. This is derived from the apparently superfluous word “two”. Since the minimum plural is two, it would have sufficed for the Torah to write just “goats” and we would know it refers to two goats. So why did the Torah include the word “two”? It teaches us that both goats must be exactly identical in appearance, height and value. Now we can understand Rabbi Shimon ben Pazi’s difficulty. Since our verse states “the two great luminaries”, the word “two” seems superfluous. It would have sufficed for the Torah to write just “luminaries” and we would know it refers to two luminaries! The word “two” teaches that “the two great luminaries” were exactly equal in size originally. Hence Rabbi Shimon ben Pazi explains why the verse later mentions “the great luminary” and “the small luminary”. Therefore, the Gemara concluded that initially they were equal in size and later God caused the Moon to shrink.