Deuteronomy 24:19-22

19At harvest time, you might forget to bring in all the crops from your fields. Do not go back to pick up all the grain. Leave it there for foreigners, widows and children who have no family. If you do that, the Lord your God will bless you in all your work.

20When you knock the olives off your trees, shake each branch only once. Leave the olives that remain for foreigners, widows and children who have no family.

21When you pick your grapes, pick only once from each vine. Leave the grapes that remain for foreigners, widows and children who have no family.

22Remember that you were slaves in Egypt. That is why I am commanding you to do all these things.