"Ali is acclaimed as the "Father of Sufism". Most of the Sufi orders claim their descent from Ali. According to Ali Hajjweri, the rank of Ali is very high in the line up of Sufism. According to Junayd of Baghdad, Ali is the Shaykh as regards the principles and practices of Sufism. … The roots of Sufism lie embedded in Islam itself. There are numerous passages in the Holy Quran which are of a mystical character. The Holy Prophet of Islam (peace be on him) himself displayed mystical inclinations and he very often retired to the cave of Hirah for the purpose of devotions, meditation and contemplation. The Holy Prophet was recipient of two types of revelations, one embodied in the Holy Quran, and the other that illuminated his heart. The former was meant for all, the latter for a selected few whose hearts could be illuminated with the Divine Light. The knowledge of the Holy Prophet was thus book knowledge (ilm-i-Safina), and heart knowledge (ilm-i-Sina). Ali got this heart knowledge from the Holy Prophet."