'Gleaning' in the Bible

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.

And he said unto them, What have I done now in comparison of you? Is not the gleaning of the grapes of Ephraim better than the vintage of Abiezer?

Yet gleaning grapes shall be left in it, as the shaking of an olive tree, two or three berries in the top of the uppermost bough, four or five in the outmost fruitful branches thereof, saith the LORD God of Israel.

When thus it shall be in the midst of the land among the people, there shall be as the shaking of an olive tree, and as the gleaning grapes when the vintage is done.

If grapegatherers come to thee, would they not leave some gleaning grapes? if thieves by night, they will destroy till they have enough.