From Rabbi Alan Ullman:

In Exodus 12:38, a "mixed multitude" left Egypt. It appears that some Egyptians left with the Israelites, thus becoming "Ivrim" or cross-overers. While Jews do not recruit converts, this verse illustrates that others can choose to become a part of the Israelite nation and story.


haggadah Section: -- Exodus Story
Source: Alisa Ente in torah study