In its discussion of the observance of Rosh Hashanah, the Torah commands in Parashat Emor (Vayikra 23:24), “Ve’hikrabtem Isheh L’Hashem” – that a special sacrifice must be offered. This refers to the Musaf offering, which is specified later in the Torah, in Parashat Pinhas (Bamidbar 29:1-6). There we read that the Musaf sacrifice on Rosh Hashanah consisted of one bull, one ram and seven sheep, all of which were brought as an Ola (burnt sacrifice). Additionally, a goat was offered as a sin-offering. The Torah there emphasizes that these are all required in addition to the monthly Rosh Hodesh sacrifice. Rosh Hashanah is observed on the first day of the month of Tishri, and thus it is also Rosh Hodesh. As such, the Musaf offering required on every Rosh Hodesh is required also on Rosh Hashanah. (And, of course, the daily Tamid sacrifice must also be offered on this day.) There is some discussion among the Rishonim as to whether the Rosh Hodesh sin-offering was also offered on Rosh Hashanah. The Rosh Hodesh Musaf sacrifice included a goat as a sin-offering, but it is unclear whether this, too, was offered on Rosh Hashanah. The verses describing the Rosh Hashanah Musaf offering state that this offering must be brought in addition to “the Ola of the [new] month” – specifying the Ola of the Rosh Hodesh Musaf offering (meaning, two bulls, one ram, and seven sheep – Bamidbar 28:11). The sin-offering of the Rosh Hodesh Musaf offering is not mentioned, perhaps suggesting that the sin-offering was not offered on Rosh Hashanah. Tosafot in Masechet Rosh Hashanah (8b) bring this view in the name of Rabbenu Meshulam, who noted the verse in Tehillim (81:4) that refers to Rosh Hashanah as “Keseh Le’yom Hagenu” – the holiday on which something is concealed. Rabbenu Meshulam explained this phrase as a veiled reference to the goat of the Rosh Hodesh Musaf offering, which was “hidden” on Rosh Hashanah, omitted from the other sacrifices offered to mark the occasion of Rosh Hodesh. Rabbenu Tam (France, 1100-1171) challenges Rabbenu Meshulam’s claim in light of a passage in the Tosefta (in Masechet Shabuot) which states that a goat for the Rosh Hodesh sin-offering was brought twelve times during the year, once every month. This clearly indicates that the goat was offered even on the first day of Tishri, Rosh Hashanah. Rabbenu Meshulam then clarified that he did not actually mean to say that the goat is not offered on Rosh Hashanah, but rather that it is not mentioned in the Rosh Hashanah prayer service, and it is in this sense that the goat is “concealed.”