How do we know that being religious without Christ is dangerous?

Jesus clearly articulates in Matthew 12:43-45 that a person engaged in religion without a genuine relationship with Him is vulnerable to deception. When the unclean spirit returns to find the person's heart empty—though they may appear reformed—the situation is worse than before because they are still under the power of sin. This demonstrates that having only an outward reformation or engagement in religious rituals cannot replace true salvation, which comes solely through Christ. Those without Christ are susceptible to spiritual binding that can multiply their condition instead of liberating them.