Ahmad published a book called The Heavenly Decree in which he challenged his opponents to a 'spiritual duel', in which the question of whether someone was a Muslim or not would be settled by God based on the four criteria laid out in the Qur'an. Namely, that a perfect believer will frequently receive glad tidings from God, will be given awareness about hidden matters and events of the future from God, most of his prayers will be fulfilled and that he will exceed others in understanding novel finer points, subtleties and deeper meanings of the Qur'an.[32]
