Albert Barnes Commentary Isaiah 17:6

"Yet there shall be left therein gleanings, as the shaking of an olive-tree, two or three berries in the top of the uppermost bough, four or five in the outmost branches of a fruitful tree, saith Jehovah, the God of Israel." — Isaiah 17:6 (ASV)

Yet gleaning-grapes ...—They shall not all be removed or destroyed. A “few” shall be left, as a man who is gathering grapes or olives will leave a few that are inaccessible on the topmost boughs or the furthest branches. Those would usually be the poorest, and so it may be implied that those left in Israel would be among the poorer inhabitants of the land.

Two or three—A very few—such as would be left in gathering grapes or in endeavoring to shake olives from a tree.

Four or five—A very few that would remain on the furthest branches and that could not be shaken off or reached.