Albert Barnes Commentary Isaiah 48:2

"(for they call themselves of the holy city, and stay themselves upon the God of Israel; Jehovah of hosts is his name):" — Isaiah 48:2 (ASV)

For they call themselves of the holy city - This refers to Jerusalem (Nehemiah 11:1; Matthew 4:5; Matthew 27:53; Revelation 21:2–27). The word translated ‘for’ here (כי, kı̂y), as it often does, means “although”; and the meaning is, although they call themselves of the holy city, they do not worship God in sincerity and truth.

Jerusalem was called ‘the holy city,’ because the temple, the ark, and the symbol of the divine presence were there, and it was the place where God was worshipped. It was considered sacred by the Jews, and they regarded it as sufficient proof of goodness, it would seem, that they had lived there. Even in Babylon, they would pride themselves on this and suppose, perhaps, that it entitled them to divine protection and favor.

And stay themselves upon the God of Israel - In time of danger and trial, they profess to seek him and to commit their cause to him.

The Lord of hosts is his name - (See the notes at Isaiah 1:9). The prophet’s purpose in mentioning his holy name here is probably to show them the guilt of their conduct.

He was Yahweh, the source of all existence. He was the God of all the hosts of heaven and all the armies on earth. How wicked, therefore, it was to come before him in a false and hypocritical manner, and, while professedly worshipping him, to be really offering their hearts to idols and to be characteristically inclined to relapse into idolatry!