Rosh Chodesh
Our parsha describes one of the most terrible events in human history - Chet Ha'Egel, or sin of the golden calf. Not surprisingly, this traumatic event is commemorated in many halachic practices.
See the beginning of the Levi Aliya of the Sedra Summary for one such custom. Now we will explain another custom, whose basis in the chet ha'egel is less obvious.
The Torah records that Aharon suggested that the men remove and bring the earrings "in the ears of your wives, your sons, and your daughters". (Shemot 32:2). But the next verse records that they brought the rings from their ears - not those of their wives. The Midrash infers that the women did not take part in the chet ha'egel. (Pirkei de Rebbe Eliezer chapter 44.)
The Midrash says that in return, women were given Rosh Chodesh as a holiday specially for them. Many women have a custom not to do work on Rosh Chodesh, and this custom is mentioned in the Yerushalmi (Taanit 1:6) and in the Tur and Shulchan Arukh (OC 417).
Some commentators add that in donating for the Mishkan the women were more eager than the men, as the Torah says (Shemot 35:22) the men came "al hanashim" - "after the women". (Tashbetz II:244.)
We will understand why Rosh Chodesh was an appropriate holiday to grant to women if we examine why there is a "Rosh Chodesh" at all. Why indeed does the moon have phases?
Rashi explains that while HaShem originally created "two great lights", seemingly equal, the moon became jealous and was punished by being diminished into the "lesser luminary". (Bereshit 1:16.) One understanding is that all along the radiance originated only with the sun. However, originally the moon was able to reflect and transmit the full might of the sun, and therefore shone like sunlight. The moon mistakenly thought that it itself could radiate light! In order to clarify matters, HaShem was obliged to diminish the moon, so that its light was both less and also varied depending on its orientation to the sun.
The human analog is that at the beginning of time the whole earth was filled with the glory of God. Every aspect of creation radiated spirituality. Ironically, it was this very profusion of Godliness that led people to mistakenly think that spirituality could originate in the material world itself. This is the error of idolatry. The first person to make this mistake was Chava. She was tempted to eat of the Etz HaDaat so that she could become "like Elokim", ignoring the fact that any elevation she would receive from the fruit must itself come from HaShem. Chava, and to a lesser extent Adam, were like the moon reflecting the light of the sun and thinking that they themselves were true luminaries!
The decree of mortality on mankind reminded us that our own spiritual radiance is only derivative. And this awareness is more acute among women who experienced an extra loss of status, becoming subordinate to their husbands. (Bereshit 3:16.)
Many men in the desert repeated the original mistake of the moon. They forgot that holiness originates only with HaShem, and thought that they could create holiness, that the golden calf which was a human invention could serve as a spiritual guide. Some even preferred this kind of "spirituality" over that of the divinely-ordained Mishkan. For them, the moon became an accuser, a reminder of their error.
The women, on the other hand, learned from the mistake of the moon. They were not fooled into thinking that we human beings have our own spiritual radiance, which shines from our own creations. They refused to take part in the making of the calf, and conversely participated eagerly in contributing to the Mishkan to demonstrate that HaShem is the source of all holiness. So for them the moon was a defender, a reminder of a hard-earned lesson.
The Tur implies that Rosh Chodesh was originally a holiday of men only, but after the chet ha'egel became a holiday of women only. Now we can understand why. Before the calf, the moon was an accuser especially to the women, reminding them of the error of Chava which paralleled that of the moon. Afterwards, the phases of the moon became a defender for the women but an accuser for the men.