Deuteronomy 24:19

24:19 Whenever you reap your harvest in your field and leave some unraked grain there, you must not return to get it; it should go to the resident foreigner, orphan, and widow so that the Lord your God may bless all the work you do.

Leviticus 19:9-10

Leaving the Gleanings

19:9 “‘When you gather in the harvest of your land, you must not completely harvest the corner of your field, and you must not gather up the gleanings of your harvest. 19:10 You must not pick your vineyard bare, and you must not gather up the fallen grapes of your vineyard. You must leave them for the poor and the foreigner. I am the Lord your God.