I will bring forth a seed out of Jacob ... — Jacob (i.e., Israel) and Judah are used to represent respectively the remnants of the two kingdoms that had been carried into captivity.
My mountains. — One of Isaiah’s characteristic phrases (comp. Isaiah 14:25; Isaiah 29:11; Ezekiel 6:2-3. Not Zion only, but every hill in Canaan was a sharer in a derived sanctity.