Charles Ellicott Commentary Isaiah 17:5

"And it shall be as when the harvestman gathereth the standing grain, and his arm reapeth the ears; yea, it shall be as when one gleaneth ears in the valley of Rephaim." — Isaiah 17:5 (ASV)

And it shall be as when the harvestman gathereth the corn. — The work of devastation is described under another image. The conqueror shall plunder the cities of Israel as the reaper cuts off the ears of corn.

With his usual Dantesque vividness, the prophet localizes the imagery. The valley of Rephaim, or, as in Joshua 15:8; Joshua 18:16, “of the giants,” lay to the southwest of Jerusalem in the direction of Bethlehem.

It was famous for its fertility, and was often for that reason attacked by the Philistines, who came to carry off its crops (2 Samuel 23:13). The prophet had looked on the reaper’s work and had seen in it a parable of that of the Assyrian invader.