Leviticus 19:9-10

9“When you harvest the crops of your land, do not harvest the grain along the edges of your fields, and do not pick up what the harvesters drop.

10It is the same with your grape crop—do not strip every last bunch of grapes from the vines, and do not pick up the grapes that fall to the ground. Leave them for the poor and the foreigners living among you. I am the Lord your God.