What is the "Olas ha'Chodesh"?
Rashi: It is the Olah of the Musaf of Rosh Chodesh, which coincides with Rosh Hashanah. 1
See above, 28:11.
Why does the Torah mention the Olas ha'Chodesh on Rosh Hashanah, but not the Chatas ha'Chodesh?
Ramban: Because having informed us that the Olah mentioned here is not the same one that is mentioned on Rosh Chodesh, 1 it is obvious that the Chatas is not the same one either.
Hadar Zekenim (citing a Midrash) and Riva: The Kaparah for all Olos is the same ? for [transgressing] an Asei, or a La'av ha'Nitak la'Asei., wheres that of the Chata'os is not - the Chatas of Rosh Chodesh atones for [Aveiros of Tum'ah] of which the owner was not aware, either at the beginning or at the endend, and of Rosh Hashanah, when there is knowledge only at the end, in which case, it is certainly different.
Ramban: Since we would otherwise have thought that the Olah mentioned on Rosh Chodesh is confined to the other eleven months, but is different on Rosh Hashanah.
