The spiritual bond between them is a miraculous force of divine illumination, and is experienced by worthy initiates of the Sufi Order; just as the electric current runs through all connected lamps and lights them. By this means the higher development is attained without great efforts. Sufism was unostentatiously practiced in Arabia during the period of Sahabis, Taba'in, and Taba'-i-taba'in. Charity, piety, spirituality, and bravery are the real proofs of Sufi advancement.