What is kuds? The answer to this question is purity. Kuds is divided into two types: essential (dhātī) and accidental (ʿaraḍī, i.e., pertaining not to the substance but to the accident). Essential kuds, for example, is the transcendence (taqdīs) of the divine presence conferred by the Name al-Quddūs, being exalted above being affected by anything from His own Essence. For to be affected implies change (taghayyur, alteration in the very essence of existence) in the one who is affected. Even if taghayyur consists in the replacement of one entity by another in a locus or space, the locus or space is thereby characterized by change. This means, for example: if a locus was yellow and became green, or was still and then moved, the locus has changed, that is, it has accepted taghayyur.
Kuds and al-Quddūs do not accept taghayyur in any way. Accidental kuds (pertaining to accidents, transitory) accepts its opposite, that is, its contrary. Human beings can only differ from one another in accidental kuds. Through ascetic discipline (riyāḍa)—that is, beautifying the nafs (the lower self) with good akhlāq (character)—through spiritual struggle (mujāhada) to refine disposition, through unveiling (mukāshafa) and contemplation (mutālaʿa) to purify the intellect, and through obedience to commands and lawful prohibitions to sanctify the limbs, these are all means of attaining this kind of kuds. The opposite of this kuds is that which is contrary to it and cannot coexist with it in the same place and time. (Futūḥāt, II, 107)
The Qur'an (al-Baqara 2:5): The Qur'an is nothing but the Essence in which all attributes are effaced. God Most High sent it down to His Prophet Muḥammad so that His witnessing in the cosmos would be one of ahadiyya (absolute oneness). This is the locus of manifestation (tajallī-gāh) named by this ahadiyya.
kurb-buʿd (proximity-distance): The meaning of this descent is as follows: The supreme reality (ḥaqīqa) of exalted ahadiyya manifested in perfection in the body of the Prophet, and from its summit, where descent and ascent are impossible (muḥāl), it descended. Only when the Prophet's body was realized in all divine realities did it become, just as his identity is the locus of ahadiyya and his essence is the locus of the manifestation of the very Essence, the locus of manifestation for the Names al-Wāḥid. For this reason, the Prophet said: "The Qur'an was sent down to me all at once." This statement of the Prophet explains that the Qur'an's descent was realized in its entirety, essentially, universally, and corporeally. This is the meaning indicated by the Qur'an al-Karīm. (Insān, I, 66)