It is the rust that forms upon the qalb (the heart). Unless it becomes deeply rooted, it only prevents the acceptance of ḥaqīqa (inner realities) and the reception of the lights of manifestation. If this rust becomes firmly established and reaches the boundary of deprivation and the level of total ḥijāb (a veil that covers all realities), as previously mentioned (Jāmiʿ), it is then called reyn or rān. (Kāshānī, 140; Jāmiʿ, 88)
(See also: reyn/rān)
sādiq fī daʿwāhu 861