For some background on the 10th c. CE Persian mystic Abul Hassan Kharqani, see this post.

The Shaikh was once asked, “What is a Dervish?”
The Shaikh replied, “A sea made from three rivers, first abstinence from sins, second generosity and third needlessness in people.” 

The Shaikh once asked a Sufi, “Who do you call a Dervish?”
The Sufi answered, “The one that has nothing in this world.”. The Shaikh replied, “Absolutely not! A Dervish is the one who has no thoughts, worries or anxieties, talks but says nothing, sees but beholds nothing, listens but hears nothing, eats but tastes nothing, has no movements or stillness, has no sorrow or happiness. This is the Dervish.”