various writers have claimed that three or four days of fasting and prayer are spiritually illuminating.
I can personally attest that a couple days of going without food can make other contributive events (such as fever, lack of sleep, etc.)
considerably more likely to result in hallucination, occasionally vivid. Given that consistent prayer, especially of the mantra type, is very much such a contributive event as well, well...
Fasting has a lengthy and fairly storied position in the ascetic arts, really. It's well known for its contribution to meditation, spirituality, tripping balls like goddamn (even without the addition of actual explicit hallucinogens or psychoactives), and so on. Often part of ritual cleansing, to allow impurities to be processed and extruded (i.e. for the kidneys and whatnot to finish up any backlog they may have been working on).
And yeah, spiritually illuminating is a good word for three or four days of fasting, little-to-no sleep, and constant or near constant prayer. You will be
out of your goddamn mind by that point, heh. You're probably going to experience vivid hallucination, strong perceptual shifts, obviously you're going to experience fairly incredible psychological effects... it's a hell of a trip. Don't even have to go that long to experience lesser symptoms, but a full go like that? Eesh. There's a
reason people saw visions when they went out in the desert for a few days, and preeeeetty likely it wasn't actually god. Human physiological and psychological reaction to that sort of scenario is pretty well known.