The Sheikh (the murshid) is a mature human being (insan-i kamil) who has walked the path to completion and is fully qualified to guide a dervish (murid) on the path. He has to be authorized for guidance by an uninterrupted chain of transmission from Hz. Muhammad (saws), the essential mature human being and the essential guide. He is the most gracious human being who has been purified to be a pure channel for the love and the grace of Allah.
The sheikh is like a doctor in his job. As a doctor treats his patients according to their specific ailments and recovering abilities, the sheikh diagnoses and treats the people who come to him in the same manner. As a commander specifies the strategy of a soldier who fights his/her enemy, so the sheikh maps the strategy for his/her fight with the false ego (nafs).
The essential ground for the relationship between the sheikh and the dervish is love. The more love the dervish feels for his/her murshid, the more effective will be the progress of the dervish.