Commentators explain that Judah's denial of God wasn't necessarily outright atheism. Instead, it was a practical denial expressed by saying, "It is not he" who speaks through the prophets. As John Calvin notes, by dismissing the warnings of judgment and believing no harm would come, they effectively stripped God of His power and role as Judge, reducing Him to a powerless phantom. This is a warning that ignoring God's threats is a form of denying His reality.