In "Kashful Mahjub", Ali Hajveri has assessed Hazrat Umar as a Sufi. The assessment of Ali Hajveri is in the following terms:
"He was specially distinguished by sagacity and resolution, and is the author of many fine sayings on Sufism."
The Holy Prophet said:
"The Truth speaks by the tongue of Umar", and again "There have been inspired Muhaddith in the peoples of antiquity, and if there be any such in my people it will be Umar."
"Retirement is a means of relieving one's self of bad company." Retirement is of two sorts; firstly, turning one's back on mankind, and secondly, entire severance from them. Turning one's back on mankind implies choosing a solitary retreat, and renouncing the society of one's fellow creatures. It also lies in seeking release for one's self from intercourse with men, and in making all people secure from one's evil actions. But severance from mankind is a spiritual state, which is not connected with anything external. When a person is severed from mankind in spirit, he knows nothing of created beings and no thought thereof can take possession of his mind. Such a person, although he is living among the people, is isolated from them, and his spirit dwells apart from them. This is a very exalted station, and Umar held that station.
Umar held this station for externally he lived among the people as their Commander and Caliph, but his spirit dwelt apart from them. His words show clearly that although spiritualists may outwardly mix with mankind, their hearts always cling to God and return to Him in all circumstances. They regard any intercourse they may have with men as an affliction sent by God; and that intercourse does not divert them from God, since the world never becomes pure in the eyes of those whom God loves.
"An abode which is founded upon affliction cannot possibly be without affliction " The Sufis make Umar their model in wearing a patched frock and rigorously performing the duties of religion."
We have it on the strength of Al-Baihaqi that in Sufist strain, Umar often said:
"Would that I were a ram, that my people might fatten me as it appeared good to them, so that when I became as fat as could be, those whom they loved might visit them, and they might kill me for them, and make part of me roast, and part of me dried flesh, and eat me, and that I were not a mortal man."