parshat Behar, Bamidbar: Mah Inyan Shemitta Eitzel Har Sinai

Parshat Behar began {Vayikra 25:1}:

א וַיְדַבֵּר ה אֶל-מֹשֶׁה, בְּהַר סִינַי לֵאמֹר.	1 And the LORD spoke unto Moses in mount Sinai, saying:
ב דַּבֵּר אֶל-בְּנֵי יִשְׂרָאֵל, וְאָמַרְתָּ אֲלֵהֶם, כִּי תָבֹאוּ אֶל-הָאָרֶץ, אֲשֶׁר אֲנִי נֹתֵן לָכֶם--וְשָׁבְתָה הָאָרֶץ, שַׁבָּת לַה.	2 Speak unto the children of Israel, and say unto them: When ye come into the land which I give you, then shall the land keep a sabbath unto the LORD.
ג שֵׁשׁ שָׁנִים תִּזְרַע שָׂדֶךָ, וְשֵׁשׁ שָׁנִים תִּזְמֹר כַּרְמֶךָ; וְאָסַפְתָּ, אֶת-תְּבוּאָתָהּ.	3 Six years thou shalt sow thy field, and six years thou shalt prune thy vineyard, and gather in the produce thereof.

Rashi asks the now-famous question, mah inyan shemitta eitzel har sinai? Rashi explains:

on Mount Sinai What [special relevance] does the subject of Shemittah [the “release” of fields in the seventh year] have with Mount Sinai? Were not all the commandments stated from Sinai? However, [this teaches us that] just as with Shemittah, its general principles and its finer details were all stated from Sinai, likewise, all of them were stated-their general principles [together with] their finer details-from Sinai. This is what is taught in Torath Kohanim (25:1). [And why is Shemittah used as the example to prove this rule, especially since the very fine details are not even specified here (Sefer Hazikkaron)?] It appears to me that its explanation is as follows: [At the plains of Moab, Moses reiterated the majority of the laws of the Torah to the Israelites before their entry into the land of Israel, this reiteration comprising most of the Book of Deuteronomy. Now,] since we do not find the laws of Shemittah [“release”] of land reiterated on the plains of Moab in Deuteronomy, we learn that its general principles, finer details, and explanations were all stated at Sinai. Scripture states this [phrase] here to teach us that [just as in the case of Shemittah,] every statement [i.e., every commandment] that was conveyed to Moses came from Sinai, [including] their general principles and finer details [and that the commandments delineated in Deuteronomy were merely] repeated and reviewed on the plains of Moab [not originally given there].

We see the following in the beginning of parshat Bamidbar, by Rashbam. On the first pasuk of Bamidbar {Bamidbar 1:1}:

א וַיְדַבֵּר ה אֶל-מֹשֶׁה בְּמִדְבַּר סִינַי, בְּאֹהֶל מוֹעֵד: בְּאֶחָד לַחֹדֶשׁ הַשֵּׁנִי בַּשָּׁנָה הַשֵּׁנִית, לְצֵאתָם מֵאֶרֶץ מִצְרַיִם--לֵאמֹר.	1 And the LORD spoke unto Moses in the wilderness of Sinai, in the tent of meeting, on the first day of the second month, in the second year after they were come out of the land of Egypt, saying:
ב שְׂאוּ, אֶת-רֹאשׁ כָּל-עֲדַת בְּנֵי-יִשְׂרָאֵל, לְמִשְׁפְּחֹתָם, לְבֵית אֲבֹתָם--בְּמִסְפַּר שֵׁמוֹת, כָּל-זָכָר לְגֻלְגְּלֹתָם.	2 'Take ye the sum of all the congregation of the children of Israel, by their families, by their fathers' houses, according to the number of names, every male, by their polls;

He notes בְּמִדְבַּר סִינַי בְּאֹהֶל מוֹעֵד and explains that this is new, in the second year -- as the pasuk states, בְּאֶחָד לַחֹדֶשׁ הַשֵּׁנִי בַּשָּׁנָה הַשֵּׁנִית. Until now, during the first year, before the Mishkan was established, all dibrot to Moshe were labelled beHar Sinai. Once the Mishkan was established, it is beMidbar Sinai beOhel Moed. He gives an interesting prooftext on the basis of the presence or lack of Nadav and Avihu in the toledot of Aharon, given that Nadiv and Avihu died during the inauguration of the Mishkan.

Also, Rashbam gives a nice reason for the count in Bamidbar. The entire point is כֹּל יֹצֵא צָבָא, which is a repeated refrain. After all, their next task is conquering eretz Yisrael. Recall that this was before the sin of the meraglim, the spies.