Kemālullāh consists of His essence. However, His essence cannot be comprehended or understood. There is no end to His perfection. Allah, Exalted is He, knows both His own essence and that His essence cannot be comprehended, and He knows that there is no end either concerning Himself or concerning anything else. That is, Allah knows His essence as it is in His own nafs (nafs, the lower self), after knowing that it cannot be comprehended by anyone else.
The intent of our statement that "He knows His own essence" is this: to Allah belongs the perfection of encompassing and unknowability. The meaning of our statement that "Allah knows His essence as it is in His own nafs, after knowing that it cannot be comprehended by anyone else" is this: it is fitting for Him in terms of His greatness and infinitude. For only that which has an end can be comprehended. Yet the Exalted Allah is endless; and it is impossible to comprehend or grasp that which is infinite. In this ḥāl (spiritual state), to comprehend His essence means to judge that the scope and core of His knowledge are worthy of being unknown. It does not mean to accept that His essence could in any way be comprehended. (Insān, I, 57)