'Grape gatherers' in the Bible

This is what the LORD of the Heavenly Armies says: "Let them glean the remnant of Israel as thoroughly as they would the vine. Pass your hand over them like grape gatherers over the branches.

"'Therefore tell them all these words, and say unto them: The LORD shall cry from above, and let his voice be heard from his holy habitation. With a great noise shall he cry from his regal court. He shall give a great voice, like the grape gatherers, and the sound thereof shall be heard unto the ends of the world.

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