A Sheikh or sheik (Arabic: شيخ shaykh; ; pl. شيوخ shuyūkh), of Sufism is a Sufi who is authorized to teach, initiate and guide aspiring dervishes. The sheik is vital to the path of the novice Sufi, for the sheik has himself travelled the path of mysticism. Viewed as the spiritual master, the sheik forms a formal allegiance (bay'a) to the disciple of Sufism and authorizes the disciple's travels and helps the disciple along the mystical path. Islamic tradition focuses on the importance of chains and legitimization. In Sufism, sheiks are connected by a continuous spiritual chain (isnad, sanad, silsila). This chain links every previous Sufi sheik, and eventually can be traced back to the Successors, and in later times to the Prophet himself. As Sufism grew, influential shayks began to acquire spiritual centers and waypoints known as  khanqah, ribat, and zaouia. Sheikhs duplicate the Prophetic realities, and are also expected to perform and act as an intermediary between the Creator and the created, since the sheikh has arrived close to God through his meditations and spiritual travels. There are several types of such sheikh.