Lubb al-lubb (the essence of the essence) is the substance of the Divine Light (Nūr). (Iṣṭilāḥ, 539)
Lubb al-lubb is the substance of the Divine Light (Nūr) by which the intellect is confirmed. For this reason, it becomes pure in the ḥāl (spiritual state) that has been stripped of the aforementioned shells, and it perceives the knowledges that are hidden from the perception of the qalb (the heart) attached to the material world and from the understanding veiled by formal knowledge. This comes from having a beautiful past that necessitates a good end (that is, being a ṣāḥib (possessor) of a life spent with righteous deeds that may help preserve iman (faith) at the last breath). (Kāshānī, 72; Jāmiʿ, 94)