Why did Hashem instruct Moshe to bring the Nesi'im's Korbanos only after they brought them in front of the Mizbe'ach?
Ramban (in Pasuk 13): Refer to 7:10:2.1:2 and note. Hashem acceded to the request of the Nesi'im and turned their good intentions into a Mitzvah 1 for all times, to inaugurate the Mikdash and the Mizbe'ach - as we find that Sh'lomoh ha'Melech made a Chanukas ha'Bayis when he built the first Beis-Hamikdash, 2 as did the Anshei Kenesses ha'Gedolah when they built the second. 3 And in the time of Mashi'ach too, there will be a Chanukas ha'Bayis for the third Beis-Hamikdash, as the Pasuk states in Yechezkel, 43:26, 27.
Ramban: Like we find by the Teme'im (regarding Pesach Sheini) earlier in chapter 9, and by the B'nei Yosef (regarding the B'nos Tz'lofchad) in chapter 36.
Ramban, See Divrei Hayamim 2, 7:5.
Ramban: See Ezra, 6:16.
QUESTIONS ON RASHI
Rashi writes that Moshe did not know if the Nesi'im would bring their Korbanos in the order of birth or according to the order in which they encamped. Why was he unsure, seeing as Hashem commanded arranged the Degalim only a month later - on Rosh Chodesh Iyar?
Mizrachi: Hashem already informed Moshe during the last forty days on Har Sinai that he would take Levi in place of the Bechoros, and about the Degalim.
Gur Aryeh: It is not necessary to say that, since the tribes already had a tradition from Ya'akov about how they would encamp, as Rashi explained above in 2:2. (Bamidbar Rabah, 2:8 states that Moshe expected the tribes to complain about the directions in which he would tell them to encamp - implying that he did not have this tradition before the command about the Degalim PF).
