פּירוש אויף בראשית 1:16

המאורות הגדולים THE GREAT LUMINARIES — They were created of equal size, but that of the moon was diminished because she complained and said, “It is impossible for two kings to make use of one crown” (Chullin 60b).

המאורות הגדולים, “the large luminaries;” according to Rashi this means that they were originally of equal size and strength. Other commentators say that the meaning of the word גדולים is that they remained as large as they had been created. Rashi also states that the moon was downsized as it had claimed that it is impossible for two queens to rule side by side with equal powers as this would lead to jealousy and friction between them. G-d agreed and suggested that the moon downsize itself in order for harmony to continue. Some commentators claim that the moon downsized itself at the beginning of each monthly orbit.

the two great luminaries: The explanation is that they are both great, nonetheless one is greater than its fellow, as it is written [concerning the sun], "the great luminary." And the rabbis interpreted midrashically [that] in the beginning, they were created equally, but [when] the moon attacked [the sun], it was reduced; and the sun retained its great size, because it heard its abuse and didn't answer. Which is like we say (Yoma 23a), "those that are insulted but do not insult, listen to their abuse and do not answer..., about them the verse is speaking [when it says] (Judges 5:31), 'and those that love Him are like the sun when it goes out in its strength,'" [meaning that they are] like the sun that heard its abuse and didn't answer, and became great through it. And also in the yotzer [prayer] on Shabbat, some have the version, "and He reduced the shape of the moon," and this is its explanation; God, may He be blessed, saw that it attacked [the sun] and He reduced it [to punish it for this]. And for those that have the version, "He saw and formed [the shape of the moon], the explanation is this; God, may He be blessed, saw that in the future, the nations of the world would make the mistake of following the sun and making it into idol worship; [and so] He stood and formed the shape of the moon [after forming the sun], to show them that the sun is not a god; since, behold, there is another sun, fitting and fine [just] like it.