Those who are demanding proof before they accept the Message have in fact rejected the Message already.
Nice circular admission to a context. Thus it's upon faith, that you rely the message to be true, not that it's truth, It's you that have to have faith, that what you read, must be literally believed. Thus admitting truth, before any evidence of the context can be proven to be reliable.
That's why the old cliche "Don't question our doctrine, to believe that it's truth you must have faith"