(Devarim 24:20) "When you beat your olive tree, you shall not cut off (lo tefa'er) after you": The early settlers would beat their olive trees and act magnanimously (with what was left on them). "your olive trees": to exclude (from peah) those of gentiles.
Gleaning Laws for Olive Trees in Deuteronomy
Sifrei Devarim 284:1