Wikipedia
Himmelsbrief
Himmelsbrief ("heaven's letter") is a name for religious documents said to have been written by God or a divine agent.
They are often said to have miraculously "fallen from sky", claim protection for owners of a copy (encouraging memetic replication) and punishment for disbelievers.
Some authors reserve the name for Christian apocryphal documents, but similar pieces are found in Islam, Hinduism and pre-Christian religions.
Hippolytus of Rome mentions one in Refutation of All Heresies (third century), and the earlier full text is a Latin one dated in the 6th century.
While preaching, Jacob, the organizer of the Crusade of the Shepherds, held one which was allegedly given by the Virgin Mary.