Most people have internal monologues.

It’s how we think things through, and usually the voice we hear, is our own. Which makes sense, because we can make it say whatever we like simply by thinking it.

But we often hear other peoples voices, too. Most common is probably the voice of a parent. You might imagine how they’ll sound when they scold you, if you think about doing something they won’t like.

It’s really not that weird that religious people claim to “hear” god. In the exact same way most people imagine what others would say in response to something they might say or do, the religious imagine how god or jesus might react.

But really, they’re just hearing their own mind frame their own thoughts in the way they picture that their religious icons might react to their thoughts and actions.

It’s not really a higher power speaking to them. They’re just interpreting the way the human mind works as supernatural, because their upbringing and belief system has them constantly asking themselves “what would god have me do” the same way we all ask “what would my friends and family have me do”.

There’s really no way to dispel this illusion, except by explaining internal monologues, and giving them time to think about it. You might also have the religious compare notes on what “god” is telling them, untill they dee how each of them hear whatever they would themselves imagine god would say. But this is something they really don’t like doing.