What is the definition of "Atzilei B'nei Yisrael"? To whom does it refer?
Rashi, Ramban, Targum Onkelos and Targum Yonasan: It means 'great men of B'nei Yisrael', 1 with reference to Nadav and Avihu and the seventy elders of Yisrael (mentioned in the previous Pasuk). 2
According to Targum Yonasan, it refers to Nadav and Avihu 'the beauiful boys' exclusively.
Ramban: And they are referred to as "Atzilei B'nei Yisrael" because the spirit of Hashem (Atzilus) rested upon them - as in Yeshayah, 41:9). See also Beha'aloscha Bamidbar, 11:25
What does the Torah mean when it writes that "Hashem did not stretch out His Hand"? Why ought He to have done so?
Rashi: It means that He did not stretch out His hand to punish them for gazing at the Shechinah even as they indulged in physical pursuits - whilst they were eating and drinking. 1
Ramban (Pasuk 13, citing Midrash Tanchuma) and Rashbam: He should have stretched out His hand to punish the Zekeinim (except for Yehoshua) for seeing visions of Elokim that they were not worthy of seeing, 2
Seforno: What the Torah means is that, Hashem did not stretch out His Hand to place them in a trance in order that they should prophesy. 3
Hadar Zekenim: Initially they were extremely afraid of being harmed. 4 But when they saw that they remained unharmed, they received the Shechinah and ate and drank amidst Simchah, which rendered them Chayav Misah.
Da'as Zekenim: It means that Hashem did not stretch out His hand to cover their faces, 5 like he did for Moshe in the cleft of the rock 6 which explains why 'they saw Elokim'.
Targum Yonasan: He did not punish Nadav and Avihu, who gazed at the Shechinah, and whose punishment was postponed until the eighth day of the Milu'im, when they died.
Riva: This is haughtiness, like one who prides himself that he may see the king every day. Or, it is familiarity with the Shechinah - the lack of awe-strickenness at what they sawad seen.
Rashbam: Like the Torah writes in Bamidbar 4:20 "ve'Lo Yavo'u Lir'os ke'Vala es ha'Kodesh, va'Meisu", and like we find by the men of Beis-SheMeish, who peeped inside the Aron and died. See Shmuel 1, 6:19. Indeed, Moshe was careful not to look at the Shechinah, when he saw the Burning Bush.
As He did with Yechezkel, 8:1, and with Shaul (Shmuel 1, 19:24), when they were on that level.
Like we find in Shoftim, 13:22, by the parents of Shimshon "Namus Ki Elohim Ra'inu" and they only saw only an angel!
Oznayim la'Torah: Because Hashem wanted them to see the sapphire brick in order to tell Yisrael what they had seen. Refer to 24:10:4.1:2. See also Oznayim la'Torah.
As the Torah writes in Ki Sisa, 33:22 "Vesakosi Kapi Alecha".
Why did Hashem not punish them?
Rashi #1: He did not want to disturb the Simchah of Matan Torah. 1
Ramban: Because they obeyed the command not to break their ranks to ascend to Hashem 2 . They looked, but remained in their places.
Rashbam: Due to the covenant into which they had entered, Hashem graciously overlooked their sin and appeared to them. 3
Seforno: To allow them to fully absorb what they had seen.
He did punish them later however - Nadav and Avihu died on the day the Mishkan was inaugurated (which was Hashem's Simchah and not Yisrael's) See Shemini Vayikra, 10:2, and the elders, in Beha'aloschs Bamidbar, 11:1, at Tav'eirah, when Yisrael grumbled about the incessant travelling (Rashi).
In Shemos 19:24.
See Rashbam.
What did they eat and drink?
Rashi #1: The Simchah over the acceptance of their Korbanos was as if they ate and drank. 1
Rashi #2 (in B'rachos 17a): They were satiated from the radiance of the Shechinah, as if they had eaten and drunk. 2
Ramban: They ate the Shelamim that were brought - in Pasuk 5, beside the Mizbe'ach at the foot of the mountain, 3 and drank (wine) to celebrate the receiving of the Torah. 4
Seforno: They made a party to celebrate the level that they had attained.
Rashbam: They sacrificed the Olos and ate the (Basar of the) Shelamim..
Refer to 24:11:151:1-2.
Refer to 24:11:151:1-2.
Ramban and Moshav Zekenim (citing the Rosh): Just as Shelamim in the era of the Beis-Hamikdash were eaten in Yerushalayim (Zevachim, 55b) and in the era of Shiloh, wherever one could see Shiloh (Ramban).
As the Torah writes in connection with the writing the entire Torah on the stones on Har Eival (See KI Savo, Devarim 27:7, and as Shlomoh did when he Hashem bestowed upon him Chochmah (See Melachim 1, 3:15) (See Ramban).
QUESTIONS ON RASHI
Rashi writes that their Simchah was as if they ate and drank. How can one compare such a spiritual beholding of the Shechinah to eating and drinking?!
P'nei Yehoshua (B'rachos 17a): The sustenance of one's 248 limbs and 365 sinews is mainly through eating and drinking. So too, their 248 limbs and 365 sinews were purified through Kabalas ha'Torah 1 and its 613 Mitzvos.
R. Chaim Tzvi Fogel: One who eats and drinks, it becomes part of his body. Also here, the Simchah became an intrinsic part of them.
The P'nei Yehoshua is explaining Rashi there. However, Rashi here comments that the Simchah was due to the acceptance of their Korbanos! (PF)