Hidden in this reciprocity, this act of correlation, is the whole secret of the invisible Guide, the heavenly Partner, the ‘Holy Spirit’ of the itinerant mystic (salik), who, needless to repeat, is neither the shadow nor the ‘Double’ as in some of our fantastic tales, but the Figure of light
Corbin defines the spirit guide in Iranian Sufism as a luminous celestial counterpart — ontologically distinct from the shadow or double — who is the necessary mirror for theophanic contemplation.
, The Man of Light in Iranian Sufism, 1971thesis