The practice of gleaning is thousands of years old; it is mentioned several times in the Bible. Leviticus 23:22 states,

And when ye reap the harvest of your land, thou shalt not make clean riddance of the corners of thy field when thou reapest, neither shalt thou gather any gleaning of thy harvest: thou shalt leave them unto the poor, and to the stranger: I am the LORD your God.

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.

We see gleaning as an early poverty program in the Book of Ruth 2:2-3;

And Ruth the Moabitess said unto Naomi, Let me now go to the field, and glean ears of corn after him in whose sight I shall find grace. And she said unto her, Go, my daughter. And she went, and came, and gleaned in the field after the reapers: and her hap was to light on a part of the field belonging unto Boaz, who was of the kindred of Elimelech.

Gleaning is a basis for Paul's seemingly harsh injunction in 2 Thessalonians 3:10

For even when we were with you, this we commanded you, that if any would not work, neither should he eat."