Albert Barnes Commentary Isaiah 30:9

"For it is a rebellious people, lying children, children that will not hear the law of Jehovah;" — Isaiah 30:9 (ASV)

That this is a rebellious people - (see the note at Isaiah 1:2).

Lying children - They had promised in solemn covenant to take Yahweh as their God, but they had been unfaithful to their vows.