Excerpt from: Sufis: The People of the Path, Vol. 1, Chapter 1
"Once a learned Mohammedan came to me and asked, "You are not a Mohammedan, then why do you speak on Sufism?"I told him, "I am not a Mohammedan, obviously, but I am a Sufi all the same."
"A Sufi need not be a Mohammedan. A Sufi can exist anywhere, in any form – because Sufism is the essential core of all religions. It has nothing to do with Islam in particular. Sufism can exist without Islam; Islam cannot exist without Sufism. Without Sufism, Islam is a corpse. Only with Sufism does it become alive.
"Whenever a religion is alive it is because of Sufism. Sufism simply means a love affair with God, with the ultimate; a love affair with the whole. It means that one is ready to dissolve into the whole, that one is ready to invite the whole to come into one’s heart. It knows no formality. It is not confined by any dogma, doctrine, creed or church. Christ is a Sufi, so is Mohammed. Krishna is a Sufi, so is Buddha. This is the first thing I would like you to remember: that Sufism is the innermost core – as Zen is, as Hasidism is. These are only different names of the same ultimate relationship with God." Osho