Which Korbanos is the Pasuk referring to?
Rashi: To the Musafim that are listed in Pinchas.
The Torah lists the Musafim in Parshas Pinchas; why does it not list them here?
Rashi: To teach us that the various parts of the Korban are not dependent upon one another - If there are no bulls, bring the rams; if there are no rams, bring the lambs.
Ramban:To teach us that Chol ha'Mo'ed is also part of the Chag inasmuch as it requires a Korban Musaf 1 ? but not with regard to the Isur Melachah, like the first and seventh days.
Seforno: To incorporate Chol ha'Mo'ed in the realm of the Musafim.
Ramban and Seforno: And the Torah does not list them here because it lists them in Pinchas.
Why does the Torah write "Shiv'as" and not 'Shiv'ah'?
Rashi: Because 'Shiv'ah' is an adjective, whereas "Shivah"is a noun - a group of seven. 1
See also Sifsei Chachamim.
What is included in "Meleches Avodah"?
Rashi (citing the Sifra): Even Davar ha'Avud (a Melachah that is crucial, and will therefore cause a loss if it is not performed today), which is permitted on Chol ha'Mo'ed, is forbidden. 1
Ramban (citing R. Chananel) and Moshav Zekenim: All Melachos that are not for Ochel Nefesh 2 but for the purpose of acquiring, such as sowing, reaping and digging. 3
Rashi (Shabbos 131b): A Melachah that entails toil. 4
Magid Mishneh (Hilchos Yom Tov 1:5): It is what a slave normally does for his master. Most people do not do it themselves, rather, they hire others to do it. This is to recall that we were slaves?
Refer to 23:8:151:1
Rashi (Sh'mos 31:15) also implies like this. Gur Aryeh (on Pasuk 8) - Melachos not done for an individual (such as harvesting) are not considered Ochel Nefesh. See Ramban, who elaborates.
This is why, wherever the Torah writes "Meleches Avodah" it is not necessary to specifically permit Meleches Ochel Nefesh.
Why does the Torah group Shabbos, [the day of Shechitas Korban] Pesach and Chag ha'Matzos in one Dibur,whereas each of the other Yamim-Tovim has its own Dibur?
Seforno: Because, as opposed to all the other Yamim-Tovim, all three were given before Matan Torah. 1
According to the Vilna Gaon (refer to 23:3:1:6), Pasuk 3 is discussing (not Shabbos but) the seven Yamim Tovim.
Oznayim la'Torah: Because the Torah already mentioned Shabbos, the Shechitas ha'Pesach and Pesach have already been discussed is Seifer Sh'mos in detail, so it only mentions them here briefly together with the other Yamim-Tovim in the Parshah of Mo'ados.
QUESTIONS ON RASHI
Rashi writes that "Meleches Avodah" refers to Davar ha'Avud, which is permitted on Chol ha'Mo'ed. The Gemara in Chagigah, 18a states that the forbidden Melachos of Chol ha'Moed are not hinted in the Torah but the Chachamim are authorized to determine what they are?
Mizrachi: Rashi cited a Sifra that said that Davar ha'Avud is forbidden on Yom Tov and permitted on Chol ha'Mo'ed. It is an Asmachta.
Refer to 23:8:4:2-4.
Rashi did not say that Meleches Avodah is Davar ha'Avud, just that even Davar ha'Avud is forbidden. (PF).
Rashi did not say it off his own bat but in the name of the Sifra.
