Albert Barnes 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 ... - This is the other figure by which the prophet describes the calamities that were coming upon Ephraim - an image designed to denote that the inhabitants and wealth of the land would be collected and removed, as the farmer gathers his harvest, and leaves only that which is inaccessible in the upper branches of the tree, or the gleanings in the field.

As when the harvester gathers the corn - The wheat, the barley, etc.; for so the word “corn” - now applied by us almost exclusively to maize - means in the Scriptures. The sense in this passage is plain. As the farmer cuts down and collects his grain and removes it from the harvest field, so the enemies of Ephraim would come and remove the people and their wealth to a distant land. This received a complete fulfillment when the ten tribes were removed by the Assyrians to a distant land. This was done by Tiglath-pileser (2 Kings 15:29), and by Shalmaneser (2 Kings 17:6).

And reaps the ears with his arm - As he collects the standing grain with one arm so that he can cut it with the sickle in the other hand. The word rendered ‘reaps’ (קצר qâtsar) means here “to collect together” as a reaper does the standing grain in his arm. The word rendered ‘ears’ (שׁבלים shı̂bălı̂ym) means here rather the spires or stalks of standing grain.

In the valley of Rephaim - The valley of Rephaim is mentioned in 2 Samuel 5:18, 2 Samuel 5:22; 2 Samuel 23:13; 1 Chronicles 11:15; and 1 Chronicles 14:9. The name means ‘the Giants,’ but why it was given to it is now unknown. In passing from Bethlehem to Jerusalem, it lies on the left, and descends gradually to the southwest, until it contracts in that direction into a deeper and narrower valley, called Wady el-Werd, which unites further on with Wady Ahmed, and finds its way to the Mediterranean. The plain extends nearly to Jerusalem, and is terminated by a slight rocky ridge forming the brow of the Valley of Hinnom (see Josephus, “Ant.” vii. 4. 1; viii. 12. 4; also Robinson’s “Bib. Researches,” vol. i. pp. 323, 324).

It seems to have been distinguished for its fertility, and is used here to denote a fertile region in general.