Deuteronomy 24:20-22

When you beat the olives from your trees, do not go over the branches a second time. Leave what remains for the foreigner, the fatherless and the widow. When you harvest the grapes in your vineyard, do not go over the vines again. Leave what remains for the foreigner, the fatherless and the widow. Remember that you were slaves in Egypt. That is why I command you to do this.