Xjyuk

Some sources indicate that not all of the Israelites left Egypt during the Exodus. On the other hand, the initial "conversion" of the Israelites to Judaism occurred at Matan Torah at Mt. Sinai during the Exodus.

Are the Israelites who stayed behind in Egypt and their descendants Jews?

I do recognize that identifying these people and especially their modern-day descendants is an exercise in genealogical futility, but suppose hypothetically that someone were to show up today at a synagogue with essentially conclusive proof that they are fully paternally and maternally descended from members of the Twelve Tribes who did not participate in the Exodus and are not maternally descended from anyone who was present at Matan Torah. What is such a person's halachic status as a Jew?

• Are they a full Jew, eligible to participate immediately on an equal standing with their brethren whose ancestors participated in the Exodus?


• Are they a full Gentile, eligible to become a righteous Noachide or seek conversion to Judaism at their discretion?


• Do they occupy some sort of halfway status, halachically Jewish but ineligible to participate in some or all mitzvot unless they "make up" what their ancestors failed to do at Sinai (e.g. through some sort of "conversion-like" process)?

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
Israelites) too have been stricken as we have”.

On Shemot 13:18 Rashi writes

Another explanation of חמשים is: only one out of five (חמשה) went
forth from Egypt, and four parts of the people died during the three
days of darkness because they were unworthy of being delivered

So it appears from Rashi that the Israelites who didn't leave Egypt died there.

1. 
   

   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.

   
   

   
   
   

   So this approach appears pretty unanimous.

   
   



2. That also depends if they all did Bris. That would certainly elevate them into the Jews category.




3. I would theorize about a different scenario: what if some families stayed at the sea or at Marah after crossing it and not going forward to Mt Sinai. I'd speculate that the Matan Torah itself wasn't a conversion event, only Torah receiving, and a Jew that didn't learn Torah is still a Jew.

Yes, after Sinai they were all Jewish.