Charles Spurgeon Commentary Isaiah 48:1

"Hear ye this, O house of Jacob, who are called by the name of Israel, and are come forth out of the waters of Judah; who swear by the name of Jehovah, and make mention of the God of Israel, but not in truth, nor in righteousness" — Isaiah 48:1 (ASV)

There always were false professors, and I suppose there always will be until Christ comes. A Judas was among the twelve apostles, and we cannot wonder that we find such in every church. But what a dreadful thing it is to wear the name of God and yet not really serve Him, to be called Christians and yet not be like Christ! It must be a very God-provoking thing to be called by His name and then insult it by not being true to it.