'Grape gatherers' in the Bible

“If grape gatherers came to you,Would they not leave some ungleaned grapes [on the vines]?If thieves came by night,Would they not destroy [only] what is enough [for them]?

“If thieves came to you,If robbers by night—How you will be ruined!—Would they not steal only until they had enough?If grape gatherers came to you,Would they not leave some grapes for gleaning?