شَهْرُ رَمَضَانَ الَّذِي أُنزِلَ فِيهِ الْقُرْآنُ
This verse indicates the greatness of the month of Ramadan. The Sufis have recorded that this is a good month for illumination of the heart because one who observes the fast has frequent experience of visions in this month. The Salat purifies the spirit and the fast illumines the heart. The purification of the spirit means that one may be delivered from passions of the self that incite to evil; and the illumination of the heart means that the gates of vision may be opened so that one may be able to behold God.
Malfuzat, Vol. IV, pp. 256–257