The Torah only mentions the Erev Rav or the Asafsuf (who might be the same people) briefly. Today Erev Rav is used a lot in some circles. But who were the Erev Rav really?
The accepted interpretation is that they were non-Jewish slaves, criminals and foreigners in Egypt who accompanied the Jews on their exodus. This isn’t impossible, but it’s not really likely. Why would Moshe have accepted a large number of foreigners on the way out? There was no conversion yet. Yitro, the first Ger only arrived around or after Har Sinai when the Torah was given. The Egyptians would not have agreed to free non-Jewish slaves or prisoners. Remember, they even chased after their Jewish slaves and only let them go after incredible devastation. And why would non-Jews have volunteered to go into the desert with no real hope of survival, and then wanted to return?
There’s a simple alternative answer that covers all these points. Who were the Mixed Multitude really? They were mixed. They were the children of Egyptian men and Jewish women. We encounter one of them as the blasphemer, but he was probably representative of the Erev Rav as a whole.
Accepted interpretations claim that he was the only such case. We know how unrealistic this is. Kohanim whose wives were in captivity had to divorce them because the halachic position is that captivity means a high probability of rape. If the Egyptians could enslave the men and kill the children, could they rape their women. Obviously yes.
When Pharaoh gave the order to kill. He only ordered the deaths of male babies. Female babies survived. His goal was to have Jewish women, while wiping out Jewish men. Egyptians obviously wanted Jewish women. The Jewish people survived his attack. Polygamy may have even been a defense mechanism against this type of ethnic cleansing. But there still would probably have been a surplus female population. And some Jews did become corrupted in Egypt. So some Jewish women may have even been voluntarily mistresses or concubines to Egyptian men.
The children of rape or even voluntary liaisons with Egyptian men would have become the Erev Rav. To the Egyptians they were Jews. To the Jews they were Egyptians. After the 10th Plague, the Egyptians may have in their panic banished anyone with Jewish blood from their country. Or the Erev Rav might have gone willingly.
But in the desert things changed. In Egypt, the Erev Rav might have held a higher status than full blooded Jews, the way that in the American South light skinned blacks of mixed race were House Slaves. But in the desert they were lower ranked. In a camp based on tribal divisions, the Erev Rav belonged nowhere. They were “rabble”, a mixed group without their own tribal leadership. They didn’t answer to anyone, and could get into all kinds of trouble. Pecking order would be established not by descent, the way it was with the tribes, but through Prison Yard showdowns.
No surprise then that the Erev Rav kept bringing up the theme of going back to Egypt. Among the Egyptians, they might have been considered Jews, but among the Jews, they started seeing themselves as Egyptians. In Egypt, they were superior because they were part of the master race. Among the Jews, they were inferior for that same reason.
And if things were bad in the desert, they were only going to get worse, if the Jews actually made it to Israel where land was allotted based on tribal divisions. Again by the father. Which is why the Erev Rav did everything it could to stop the Jews from getting there. What the Erev Rav wanted most of all was to get back to Egypt. But they settled for sabotaging any progress the Jews made along the way. Because any progress in Jewish nationhood would set back their status even more, and make it harder to push for a return to Egypt.
There’s no way to know how large the Erev Rav was. But even a 1000 men with no leadership structure and a sense of grievance can do a lot of damage.
In more modern times, Erev Rav came to mean any fifth column or foreign element among the Jews. Today It usually means people who might be biologically Jews or members of the Jewish community, but whose real allegiances lie elsewhere. This is what makes them “mixed”. They have a mixture of Jewish ethnicity but alien loyalties. And this makes them act as a fifth column, obstructing and sabotaging the Jewish people.
Erev Rav is used today for everyone from Jewish anti-Israel activists to Jewish leaders who pursue goals not in the interests of their communities. It doesn’t mean that their parentage is mixed, but that their loyalties are. The Erev Rav were living together with the Jewish people, but not part of it. In the same way the Erev Rav today is part of the Jewish community, but has a different destination in mind.