This song is about people who interpret the Grateful Dead's music as divine and see themselves a "prophet" for said divinity. The Dead have (or at least had) a great many fans who take their music a bit too seriously. You could, perhaps, call them zealots. Members of the band were often a little freaked out by this crazy type of fan. Bob Weir and John Barlow decided to pen a song about it. However in typical Grateful Dead fashion the song is highly nuanced. So much so that most people who hear the song don't understand its meaning. This is great example of the way lyrics to Grateful Dead songs operate on such a sophisticated level. While lots of fans write songs about crazy fans the song meaning is rarely veiled.
According to Weir while on the road they would skip through the Bibles that were in hotel rooms. One night Garcia called Weir and told him to check out the books of Ezekiel and Daniel, they thought it was a reference to aliens visiting earth and other interesting strange things, so the song was wrote about that and people that would meet them after shows and share their spaced out trip experiences. Some of these people were so persistent it got annoying, so part of what Weir is singing is "I have heard it all before so please keep your mouth shut”.
From: https://songmeanings.com/songs/view/47670/
