I’m not saying it isn’t silly, but it comes from a specific passage in Mark 16-

16 Whoever believes and is baptized will be saved, but whoever does not believe will be condemned.

17 And these signs will accompany those who believe: in my name they will cast out demons; they will speak in new tongues;

18 they will pick up serpents with their hands; and if they drink any deadly poison, it will not hurt them; they will lay their hands on the sick, and they will recover.”

So Big J, who’s also Big G, says that if you believe, you’ll be able to walk around with snakes and drink poison and survive.

They’re not so big on the poison drinking, admittedly.