Although many good answers exist here already, I want to provide somewhat of a more comprehensive response (as best as I can) by putting all the answers I know of in one place.
There are three overall ways to answer the question "why do we associate Shavuos with Matan Torah if that is not how it is presented in Tanakh?" One can respond either (I) by saying ...
Rashi on Shemot 10:22 writes regarding the plague of darkness
And why did He bring darkness upon them? Because there were wicked
people amongst the Israelites of that generation who had no desire to
leave Egypt, and these died during the three days of darkness so that
the Egyptians might not see their destruction and say, “These, (the
As Alex shared this was the same generation: the first census was before the Tabernacle was built since the half-shekels used for the count were used for the sockets of the structure, the second was seven months later.
Still Artscroll picks up on the fact the numbers are similar and brings 3 opinions
Rashi (Shemot 30:16) responds that for the purpose of ...
Gittin 60a (as explained by Rashi):
בעא מיניה אביי מרבה ... למאן דאמר תורה מגילה מגילה ניתנה
תיבעי למאן דאמר תורה חתומה ניתנה
alludes to a debate as to whether the Torah was written down one paragraph at a time throughout the stay in the desert, and then put together at the end of the forty years, or was only written down for the first time, in one go, ...
Your question comes from two points, that:
(a) Halachos L'Moshe MiSinai are not hinted to in the Torah
(b) that these halachos are therefore outside of and external to the Torah, and the completeness of the Torah would not allow for such a thing.
In terms of the first point, while that is clearly the opinion of the Rambam in his Introduction to the ...
'The Rabbis point out that all the precepts of the Decalogue had been practised by the Patriarchs and had become the family tradition of their children' (Rabbi Joseph H. Hertz, The Pentateuch and Haftorahs, p. 403). This granted, the chiddush in Shemot 20+ is that (1) God Himself, accompanied by angels, comes down from Heaven and speaks the Ten Commandments ...
The short answer to your paraphrased question, "Does traditional Judaism believe that Angels still keep the Torah today?", is yes. But their keeping is not like our keeping.
The key to understanding this is to realize that angels do not keep the Torah in the same way as human beings. In fact, this was the original proof which was given by Moshe Rabbeinu ...
Sefer Shaare Ora, first Shaar. "Below the name A.D.N.I., (א-ד-נ-י), is the world of perud". The hataot Maor Yosef says.
הם העולמות שתחת מלכות דאצילות, והם עולם בריאה יצירה עשיה
Olam haperud is the set of worlds Bria, Yetsira, Asia, they are below malchut deatsilut, the lower expression of world of atsilut.
The Torah is (seemingly) explicit that all G-d's servants left Egypt (Exodus 12.41):
וַיְהִי מִקֵּץ שְׁלֹשִׁים שָׁנָה וְאַרְבַּע מֵאוֹת שָׁנָה וַיְהִי בְּעֶצֶם הַיּוֹם הַזֶּה
יָצְאוּ כָּל־צִבְאוֹת ה' מֵאֶרֶץ מִצְרָיִם׃
at the end of the four hundred and thirtieth year, to the very day, all the ranks of the LORD departed from the land of Egypt.
[Chabad.org says in The Mikvah
The world’s natural bodies of water—its oceans, rivers, wells and
spring-fed lakes—are mikvahs in their most primal form. They contain
waters of Divine source, and thus, tradition teaches, the power to
This status implies that the Well of Miriam would have served. Indeed the same article states explicitly:
The first step of the answer: Shemos 24:4:
וַיִּכְתֹּ֣ב מֹשֶׁ֗ה אֵ֚ת כָּל־דִּבְרֵ֣י ה' וַיַּשְׁכֵּ֣ם בַּבֹּ֔קֶר וַיִּ֥בֶן מִזְבֵּ֖חַ תַּ֣חַת הָהָ֑ר וּשְׁתֵּ֤ים עֶשְׂרֵה֙ מַצֵּבָ֔ה לִשְׁנֵ֥ים עָשָׂ֖ר שִׁבְטֵ֥י יִשְׂרָאֵֽל׃
Moses then wrote down all the commands of the LORD. Early in the morning, he set up an altar at the foot of the mountain, with twelve ...
One could easily argue that they were fully Jewish not on the 7th of Sivan, but on the 4th. After all, we learn the halachos of conversion from Har Sinai (Yevamos 46b), and, according to R’ Yosi, they washed their clothes, toveled, and sprinkled on the 4th of Sivan, and so they had to have three days (Shabbos 86b-87a).
The Gemara ibid. 86a makes this point ...
It was the same generation. As the verses in Numbers 1:1-2 say when introducing the count:
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:
'Take ye the sum of all the congregation of the children of Israel, ...