James 2:19 – "You believe that God is one. You do well. The demons also believe, and shudder.”
James is talking about how important that our faith is alive and results in works. We are not saved by works, but if saving faith is in us, then righteous works will surely be the fruit of that salavation.
Here, an example is made of the demons. They too believe that God is One. They have a form of ‘faith’ but their actions prove that it’s a dead faith.
If our faith doesn’t result in righteous actions, then really, we’re no better off than the demons.