Jamieson, Fausset and Brown on Isaiah 1:9

9. Jehovah of Sabaoth, that is, God of the angelic and starry hosts (Psa 59:5; 147:4; 148:2). The latter were objects of idolatry, called hence Sabaism (2Ki 17:16). God is above even them (1Ch 16:26). "The groves" were symbols of these starry hosts; it was their worship of Sabaoth instead of the Lord of Sabaoth, which had caused the present desolation (2Ch 24:18). It needed no less a power than His, to preserve even a "remnant." Condescending grace for the elect's sake, since He has no need of us, seeing that He has countless hosts to serve Him.