Have you ever wondered why, in the Mussaf Amidah of a Jewish leap year (when there are two Adars), we add the phrase ulichaparas posha, “and for atonement for sin”? It is a 13th phrase in the list of brachos at whose end it is added, which makes sense for a year with 13 months. But why “atonement of sin”? The Nachlas Tzvi has a fascinating suggestion.

Our parsha lists a number of special communal korbanos. On Rosh Chodesh, the day of the new moon, among other sacrifices, a chatas, a sin-offering, is brought (Bamidbar 28:15).  Unlike other chata’os brought on holidays, though, it alone is called a chatas laHashem. The halachic import of that fact, as Rashi notes, is that it atones for tum’ah contamination of the mikdash or kodoshim that no person ever knew about, only Hashem.

But the Midrash (also cited by Rashi) says something flabbergasting, that the korban is brought as an “atonement” – whatever that might mean – on behalf of Hashem, for His having “lessened” the moon. The reference, of course, is to the Midrash’s account of how the moon complained that “two kings cannot wear one crown” and, as a result, was divinely demoted.

The reason for a Jewish leap year, says the Nachlas Tzvi, is that the Jewish calendar, which is essentially lunar, requires an occasional additional month, to bring the Jewish months into alignment with the seasons (which are the result of the sun’s rays’ angle toward the hemispheres of an axis-tilted earth). The Nachalas Tzvi suggests  that the “lessening” of the moon may refer not only to a muting of brightness or size but also to the fact that it takes less time for our satellite to orbit around the earth 12 times than it takes the earth to revolve around the sun, rendering a lunar year “less,” in a temporal sense – shorter – than a solar one.

He sees the “atonement” as being for the moon’s complaint. But it would seem that it might better refer to the confounding Midrash cited that Rashi cites, whatever it might mean.

© 2025 Rabbi Avi Shafran