Isa 27:12

27:12 thresh. This verb can refer to separating grain (by flailing the stalks, Ruth 2:17) or olives (by beating the branches, Deut. 24:20). It is frequently used as a metaphor for separating and gathering God’s people from the world.

river . . . Brook. That is, the Euphrates River and the Wadi el-Arish, defining the boundaries of the territory of Canaan, given by promise to Abraham (Gen. 15:18). Assyria and Egypt will be connected by a highway (11:16; 35:8, 9) that leads from both to Jerusalem. People from different origins will be united in worship of the one God.