Jamieson, Fausset and Brown on Isaiah 39:3

3. What ... whence--implying that any proposition coming from the idolatrous enemies of God, with whom Israel was forbidden to form alliance, should have been received with anything but gladness. Reliance on Babylon, rather than on God, was a similar sin to the previous reliance on Egypt (Is 30:1-31:9).

far country--implying that he had done nothing more than was proper in showing attention to strangers "from a far country."