Babylonian Talmud, Chullin 60b

“And God made the two great lights,” but later it says: “the great light and the lesser light”! The moon said before the Holy One: Master of the world, is it possible for two rulers to share [literally: “to use”] one crown? God said to her: Go and diminish yourself! She said before God: Because I asked a good question, I should diminish myself? God said: Go and rule both in day and in night. She said: What advantage is that? A candle in the daylight is useless. God said: Go and let Israel count their days and years by you. She said: They use the daylight [of the sun] to count seasonal cycles as well...Seeing that she was not appeased, the Holy One said: Bring a (sacrificial) atonement for me that I diminished the moon! This is what Rabbi Shimon ben Lakish said: What is different about the ram of the new moon that is offered “for God”? Said the Holy One: This ram shall be an atonement for me that I diminished the moon. [Translation by Rabbi Steve Greenberg]