Therefore thus saith the Lord GOD of hosts, O my people that dwellest in Zion, be not afraid of the Assyrian: he shall smite thee with a rod, and shall lift up his staff against thee, after the manner of Egypt.
Therefore - Return to the main proposition, Assyria's ultimate punishment, though employed as God's 'rod' to chastize Judea for a time.
O my people - God's tenderness toward His elect nation.
Be not afraid of the Assyrian: he shall ... lift up his staff against thee, after the manner of Egypt - as Egypt and Pharaoh oppressed thee. Implying, too, as Israel was nevertheless delivered from them, so now it would be from the Assyrian Sennacherib. The antithesis in Isaiah 10:26, end, requires this interpretation.