Deuteronomy 24:20-22

When thou beatest thine olive-tree, thou shalt not go over the boughs again: it shall be for the sojourner, for the fatherless, and for the widow. When thou gatherest the grapes of thy vineyard, thou shalt not glean it after thee: it shall be for the sojourner, for the fatherless, and for the widow. And thou shalt remember that thou wast a bondman in the land of Egypt: therefore I command thee to do this thing.