I and the children … are for signs. Isaiah's children seem to have been "for signs," especially in respect of their names. Shear-Jashub meant "A remnant shall return" (Isaiah 10:21), and thus held out two hopes; one that a remnant of Israel would return to God and become his true servants, another that a remnant would return from the captivity that had been prophesied (Isaiah 5:13).
Maher-shalal-hash-baz—"Plunder speeds, spoil hastens"—was a "sign" of a different kind. Primarily, his name referred to the spoiling of Damascus and Samaria (verses 3, 4); but it may further have indicated a time of general disturbance, plunder, and ravage.
It is not quite clear in what respects Isaiah was a "sign." Perhaps he, too, in his name, which meant "(Our) salvation is Jehovah"—certainly also in his symbolical acts (Isaiah 20:3), and possibly in the firmness of his faith, which never wavered.
From the Lord of hosts; literally, from by the Lord of hosts—an expression like the French de chez. God had supernaturally appointed the sign in one case (verses 1-4), but in the other two had merely brought them about by the secret working of his providence.
But the prophet treats all three as coming equally from him. Which dwelleth in Mount Zion. Hero, again, is encouragement. God has not quitted Zion. The Shechinah still rests between the cherubim in the holy of holies.
While this is so, God is still with his people (Immanuel).