Who were the "Na'arei B'nei Yisrael", whom Moshe sent to bring Korbanos?
Rashi, Rashbam, Targum Onkelos and Targum Yonasan: They were the Bechorim. 1
Ramban #2: It refers to the youths who had never tasted the taste of sin (who had never been intimate with a woman). 2
Rosh: They were Sheluchim (emissaries) - not necessarily young ones. 3
Targum Yonason: Seeing as the Mishkan had not yet been erected and the Kohanim had not yet been chosen. Ramban (citing Targum Onkelos) - they are called Na'arim, in contrast to "the elders" (Pasuk 9), to show that they were not sent due to their Chochmah, but because they were Bechorim. Refer to also to Bamidbar, 8:17:1:4 - regarding the choosing of the Bchorim before the Mishkan was built.
Since they are holy and worthy of bringing sacrifices. See B'rachos, 43b/ (Ramban).
Like we find in Melachim 2, 5:20, "Gechazi Na'ar Elisha", even though he already had three grown-up sons, in Shemos 33:11 where the Torah writes "Yehoshua Bin Nun Na'ar" (even though he was fifty-six), and in Vayeira Bereishis, 22:3 "Sh'nei Ne'arav" of Avraham (even though Yishmael was thirteen. Rashi says that the other 'Na'ar' was Eliezer, who helped fight the four kings sixty-two years earlier (based on Tosfos Shabbos 10b DH 've'Shel').
Why does the Pasuk refer to the firstborn as 'Na'arim'?
Ramban: In contrast to "the Zekenim" mentioned in Pasuk 9.
What was the significance of the Olos and Shelamim that they sacrificed?
Chagigah, 6a: According to Beis Hillel, the Olos comprised the Korban Tamid, 1 and the Shelamim, a Korban Chagigah. 2
Either "Olos" in the plural, refers to the Tamid shel Boker and the Tamid bein ha'Arbayim, or it refers to the Tamid shel Shachar exclusively, which explains why "Olos" is spelt minus the 'Vav', implying that they brought only one Korban.
In fulfilment of Moshe's statement to Par'oh - citing Hashem - "Veyachogu Li ba'Midbar". See Oznayim la'Torah on Pasuk 10 DH 've'Sachas Raglav'..
If the Shelamim were bulls, what were the Olos?
Yoma, 22b: The Olos were lambs. 1
Torah Temimah, note 4, explains that according to others, also the Olos were bulls - even according to Beis Hillel, who maintain that the Olos comprised the Korban Tamid - See Oznayim la'Torah.
Why did Yisrael bring specifically bulls as Shelamim?
Ramban: Because, throughout their sojourn in the Desert, they were afraid of the Midas ha'Din, 1 which the bulls represent 2 - so thry brought bulls to counter the Midas ha'Din.
In fact, this was the source of their mistake in building the Golden Calf (based on the fact that they were currently in the desert - a location of destruction and desolation - R. Bachye) as the Ramban explains in Ki Sisa, Sh'mos 32:1 DH 've'Hinei Aharon' (only there, he ascribes the choice of a calf to Aharon).
Hence we find that the most serious offences required a bull as an atonement - See for example, Vayikra, 4:3, and 4:14, and Sh'lach, Bamidbar 15:24, and that is also the underlying reason for the Parah Adumaah (Ramban).
How will we reconcile the current Pasuk with the opinion that, until Matan Torah, Yisrael did not bring Shelamim (only Olos)?
