"va'Asisem Isheh". Does this mean that, upon entering Eretz Yisrael, everyone is obligated to an Olah or a Shelamim?
Rashi and Ramban: What the Torah means is that, upon entering Eretz Yisrael, if a Yachid wants to bring a Korban Neder or Nedavah, then it must be accompanied by a Minchas Nesachim. 1
Implying that, in the desert, a Korban Yachid did not require Nesachim - like the opinion of R. Yishmael in Zevachim, 111a. See Ramban.
Why does the Torah need to specify "Olah O Zevach"?
Menachos, 90b: The Torah writes "Olah" to preclude a Minchah from Nesachim, "Zevach" to include a Shelamim and "O" to include a Korban Todah. 1
See Torah Temimah, note 3.
What are the implications of "Lefalei Neder O Nedavah"? Having written "Olah O Zevach", why does the Torah need to add it"?
Rashi (in Sotah, 15a): It implies that only a Korban Neder or Nedavah 1 requires a Minchas Nesachim, but not a Chatas or an Asham. 2
Menachos, 90b: To teach us that any Korban that comes as a Neder or a Nedavah requires Nesachim.
Menachos, 91a: To Darshen a K'lal u'Perat u'Chelal: "Va'asisem Isheh la'Hashem" - K'lal; "Neder O Nedavah" - P'rat; "le'Re'ach Nicho'ach" - K'lal, to incorporate the babies of Kodshim, their Temuros, the leftovers, 3 Ashamos that are placed in a field to obtain a blemish 4 and Kodshim that were Shechted she'Lo li'Sheman, and to preclude whatever is obligatory - B'chor, Ma'aser, Pesach, Chatas and Asham. 5
Oznayim la'Torah: To teach us that the Parshah is referring to Korb'nos Yachid 6 (which would come into effect only after they entered Eretz Yisrael), which explains the D'rashah in 15:3:4:1.
Having written "Lefalei Neder O Nedavah", why does the Torah need to insert "Olah O Zevach"?
Menachos, 91a: Because if not for "Olah O Zevach", we would have precluded Olos Chovah and Shalmei Chovah from Nesachim, from a K'lal ("Va'asisem Isheh la'Hashem") u'Perat ("Lefalei Neder O bi'Nedavah") u'Chelal ("le'Re'ach Nicho'ach").
See Torah Temmah, note 5.
Why does the Torah insert the word "Lefalei Neder O Nedavah"?
Menachos, 90b: Because we would otherwise have thought that one is only Chayav to bring Nesachim if one sacrifices a Neder and a Nedavah, but not for one without the other.
Why does the Torah need to mention "O be'Mo'adeichem" independently?
Rashi: Because the Korbanos of Yom-Tov (the Olas Re'iyah and Shalmei Chagigah - Menachos, 90b) are not voluntary but obligatory. 1
Menachos, 91b: To teach us that an Olah and Shelamim as a Neder or as a Nedavah, one is Chayav to bring two Nesachim, one for each. 2
And which would therefore be precluded from Nesachim - Refer to 15:3:1.2:1. See also Sifsei Chachamim and Torah Temimah, note 9. It is not however, clear why do not already know this from "Olah O Zevach" - Refer to 15:3:1.3:2.
See Torah Temimah, note 10.
What happens to the Minchas Nesachim?
Rashi: The Minchah, including the oil that is mixed together with it, is burned on the Mizbe'ach, and the wine poured into the bowls on top of the Mizbe'ach.
Having written "Zevach", why does the Torah need to insert "min ha'Bakar O min ha'Tzon"?