Is there such a thing as Du`a Kanz il-‘Arsh?
Question

I have come across a supplication called "kanjil arushu" in some books which is recited as follows:  
Lailaha illallahu subahanal malikil kuddose , Lailaha illallahu subahanal azizul jabbaru , Lailaha illallahu subahanal raufi rahim.....etc
I want to know if this is a known supplication and what are the virtues of reciting it.
Praise be to Allah.This du`a is not known in the books of Sunnah. It seems most likely that it has been fabricated by some of the Sufis in what they call al-awraad, which is a collection of du`as and words that are compiled for the mureeds (followers of a Sufi shaykh) to recite at certain times in a certain manner and for a certain number of times. Undoubtedly it is not permissible to follow them in the awraad that they fabricate. “Du`a is an act of worship,” as the Prophet (peace and blessings of Allah be upon him) said, and the basic principle concerning acts of worship is tawqeef i.e., stopping at what has been narrated in sharee’ah (and not inventing anything new).  
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said: 
Undoubtedly dhikr and du`as are among the best kinds of worship. Acts of worship are based on tawqeef and following, not on whims and desires and innovation. The du`as and dhikrs narrated from the Prophet (peace and blessings of Allah be upon him) are the best that anyone can find of dhikr and du`a, and the one who limits himself to them will be safe and sound. The beneficial results that they bring cannot be put into words or fully comprehended by man. Any other dhikrs may be haraam or they may be makrooh. They may involve shirk which most people may not realize and which would take too long to explain in detail. 
No one has the right to prescribe for people any kind of dhikr or du`a that is not narrated in the Sunnah and make it an act of worship that people should perform regularly as they perform the five daily prayers regularly. Rather this is a kind of innovation in religion for which Allah has not given permission… As for adopting a wird that is not prescribed in sharee’ah and dhikr that is not prescribed in sharee’ah, this is something that is forbidden. Moreover the du`as and adhkar that are prescribed in sharee’ah are are the best and lead to achieving all aims and goals; no one turns away from them and adopts innovated and invented adhkar except one who is ignorant, negligent or a wrong doer. 
Majmoo’ al-Fatawa, 22/510- 511 
See also the answer to question no. 6745 which contains more information. 
And Allah knows best.