Summary: Dealing with thoae who try to sabotage the church and the children of God
I will sing of the mercies of the LORD for ever: with my mouth will I make known thy faithfulness to all generations.
And a mixed multitude went also with them, and very much livestock, both flocks and herds.
And the mixed multitude among them [the rabble who followed Israel from Egypt] began to lust greatly [for familiar and dainty food], and the Israelites wept again and said, Who will give us meat to eat?
Who are mixed multitudes?
When the Israelites journeyed from Rameses to Succoth, the first stage of the exodus from Egypt, there were up with them "a mixed multitude." (Exodus 12:38 (quickview) Numbers 11:4 (quickview) ) They were probably the offspring of marriages contracted between the Israelites and the Egyptians; and the term may also include all those who were not of pure Israelite blood. In Exodus and Numbers it probably denoted the miscellaneous hangers-on of the Hebrew camp, whether they were the issue of spurious marriages with Egyptians or were themselves Egyptians, or belonging to other nations. The same happened on the return from Babylon, and in (Nehemiah 13:3 (quickview) ) (compare with Nehe 13:23-30) a slight clue is given by which the meaning of the "mixed multitude" may be more definitely ascertained.
In Jeremiah 25:20 (quickview) And all the mingled people, and all the kings of the land of Uz, and all the kings of the land of the Philistines, and Ashkelon, and Azzah, and Ekron, and the remnant of Ashdod,
Jeremiah 50:37 (quickview) , A sword is upon their horses, and upon their chariots, and upon all the mingled people that are in the midst of her; and they shall become as women: a sword is upon her treasures; and they shall be robbed.
"mingled people" is a term of contempt for the hybrid blood of certain of Israel's enemies.
Exodus 12:37 (quickview)  gives us our first “census” of the population of Hebrews who left Egypt for the Land of Promise. We are told that around 600,000 men departed from Ramses, not to mention children and, presumably, women. Some conservative estimates have suggested that, even by placing just one woman and one child with each man, the numbers would swell to nearly 2 million. And, if we learned anything about the typical Jewish families from the Book of Genesis, we can safely assume that being an only child was a rarity. More realistic approximations have been made by scholars of anywhere from 3 to perhaps as many as 6 million Hebrews leaving Egypt in the Exodus, although we really have no way of knowing for sure.
One thing we do know from the text, a “Mixed Multitude” accompanied the Twelve Tribes of Jacob as they set out toward Palestine. Neither fully Jewish nor fully Egyptian, these racially mixed people were the sons and daughters of one Hebrew parent and one Egyptian. The product of two separate and competing cultures, these “half-breeds” were perhaps too Egyptian to really fit in with the Children of Israel, and definitely too Jewish to be completely comfortable among their Egyptian brethren.
A portrait of those even to this day who divide and subvert the Body of Christ from within, the mixed multitude were those with split loyalties, coming close to the presence of God yet never fully committing to Him. These were the people who pined for the things they left behind in Egypt whenever times grew tough, the first to grumble and complain when hardships arose. They were an ever-present source of trouble and discord among the Hebrews, eroding the morale of the entire nation by their own negativity.