Vessels of conversation

After concluding prayers at the YHSTC Minyan this morning an interesting discussion began to brew. I was still in the middle of my personal devotions, so I missed the the beginning, but I'm happy (I won't vouch for anyone else) to report that I nevertheless contributed a new understanding to the issue under consideration. I will now try to recreate the conversation for your edification.

RMF: Who was learning in the Beis Medrash that Yehuda set up for the children of Israel before they were enslaved in Egypt?
TRS: The Levites. Instead of helping their brethren who were slaving away, they stayed inside and learned Torah, much like the Chareidim of today who refuse to serve in the army or get normal jobs.
RM: What were they learning? The Torah had yet to be given.
TRS: Sefer Yetzirah, written by Adam, the first man.
RM: Really? The whole day?
TRS: What else did they have to learn? And anyway, what's wrong with learning it the whole day? It's a big book.
RM: I've tried learning the Sefer Yetzirah, and believe you me, if you learn it for more than an hour, you go crazy.
TRS: Exactly. And now we understand why the Egyptians put the Jews to work. They weren't trying to enslave them, they were just trying to help all these insane people do something productive. The same thing is done in our times too: in prisons, homes for the blind, and I'm sure in mental asylums also. The Jews were just ungrateful.

In the interests of full disclosure, I am forced to say that in truth I assume that the Jews just learned the Torah. If Abraham, Isaac, and Jacob could keep the Mitzvos without having been at Mount Sinai (unless there was some really weird time warp shtuff going on there), then why couldn't they learn Torah all day also? Sure, they probably learned Sefer Yetzirah also sometimes, but that was just for fun.

A bit later another question was asked, and I had to give the standard answer, since I couldn't think of a funny one. Why did the Jews have to eat milk after the giving of the Torah? Why couldn't they Shecht some cows and beef out? The answer is that their keilim, their vessels, were not Kosher. Why not? Because they had been used for non-Kosher meat. Why was the meat not-Kosher? Because the people who slaughtered it weren't Jewish. Why were they not Jewish? Because the Torah had not been given. Put it this way: If you went back in time to visit Moses before the giving of the Torah, you wouldn't eat in his house.

I now have a question for all of you, my faithful readers. The Rebbe asks the following question in a Sicha: Why does the Siman in Shulchan Oruch dealing with the laws of Shavuos not have its own heading? Why does it come under the laws of Pesach? The Alter Rebbe even finishes off his treatment of these laws by proclaiming, "This concludes the laws of Pesach". As far as I recall, the Rebbe begins by saying that we can't answer that the reason is because there are very few laws, because other subjects with an equally small number of laws do get their own section. The real answer is that Pesach and Shavuos are intrinsically connected. How? That's what I don't recall. My real problem is that I can't remember where the Sicha is, and I'd surely appreciate if anyone has any information that can lead to its arrest.