Deuteronomy 24:18-19

But thou shalt remember that thou wast a bondman in Egypt, and the LORD thy God redeemed thee thence: therefore I command thee to do this thing.

When thou cuttest down thine harvest in thy field, and hast forgot a sheaf in the field, thou shalt not go again to fetch it: it shall be for the stranger, for the fatherless, and for the widow: that the LORD thy God may bless thee in all the work of thine hands.