Charles Ellicott Commentary Isaiah 27:12

"And it shall come to pass in that day, that Jehovah will beat off [his fruit] from the flood of the River unto the brook of Egypt; and ye shall be gathered one by one, O ye children of Israel." — Isaiah 27:12 (ASV)

The Lord shall beat off ... —The English Version conveys hardly any meaning. The verb used is the one we find in Isaiah 28:27 for the “beating out” of seeds from their husks, as a form of threshing. In Deuteronomy 24:20 it is used of the beating down of the olive crop.

So understood, the words imply a promise, like that of Isaiah 17:6, but on a far wider scale. Instead of the gleaning of a few olives from the topmost branches, there should be a full and abundant gathering, and yet each single olive, “one by one” should receive undivided care. Judah and Israel should again be peopled as in former times, and the ideal boundaries of their territory should be restored.

The channel, or flood of the river, is the Euphrates.

The stream of Egypt. —As in Genesis 15:18, 1 Kings 8:65, not the Nile, but the river that divides Palestine from Egypt, known by the Greeks as Rhinocolura, and now the Wady-el-’Arish.