" ...If your purpose is religious, to tell us about God’s love or convince us we need Jesus to be our personal savior, please don’t knock. Instead, bow your head and pray as sincerely and intently as possible for this door to disappear. When it does, feel free to come on in...we will definitely want to hear what you have to say!"
Now here's where the revelation thing comes in...
I have seen at least a dozen different religious types...usually with bible in tow...walk up to my front door, full of the holy spirit and determined to win a convert for their particular god or version thereof, only to stop, read my little sign, then turn and quietly depart.
If they really believed they served an omniscient god who answered prayer, why leave? Why not bow their heads and pray for my door to disappear?
The only answer possible is that not a single one of them had nearly as much faith in their god and his powers as they would have others believe. When the best opportunity they'd ever had to prove everything they claim about their god presented itself they faltered, unwilling to put their faith to a real test.