In the time of Alexander the Macedonian, the egyptians came to him with a complaint against the jews quoting the Torah (exodus 12:36) 'And the LORD gave the people favour in the sight of the Egyptians, so that they let them have what they asked. And they despoiled the Egyptians.'. and we want it back.
Geviha Ben Pesisa, a Jew requested of the scholars of the time 'allow me to reply to them, if I lose you can say he wasn't a scholar. Should I win please say that it was the Torah of Moshe that carried the argument.'
Geviha then asked the Egyptians where is your proof? they replied your Torah (verse above). Geviha answered, then I will to use the torah, does it not say (exodus 12:40) 'Now the time that the children of Israel dwelt in Egypt was four hundred and thirty years.' you owe us for the labor of 600,000 people that you enslaved for 400 years.
Alexander gave the Egyptians 3 days in which to refute Geviha's answer. They never returned, leaving behind all their fields in Israel. That year being a sabbatical year (shmita) when all fields lay fallow, these abandoned fields were a boon for the Jews.