They are the followers of Sahl b. `Abdalláh of Tustar, a great and venerable Ṣúfí, who has been already mentioned. His doctrine inculcates endeavour and self-mortification and ascetic training, and he used to bring his disciples to perfection in self-mortification (_mujáhadat_). It is related in a well-known anecdote that he said to one of his disciples: “Strive to say continuously for one day, ‘O Allah! O Allah! O Allah!’ and do the same next day and the day after that,” until he became habituated to saying those words. Then he bade him repeat them at night also, until they became so familiar that he uttered them even during his sleep. Then he said: “Do not repeat them any more, but let all your faculties be engrossed in remembering God.” The disciple did this, until he became absorbed in the thought of God. One day, when he was in his house, a piece of wood fell on his head and broke it. The drops of blood which trickled to the ground bore the legend “Allah! Allah! Allah!” The “path” of the Sahlís is to educate disciples by acts of self-mortification, and austerities; that of the Ḥamdúnís[114] is to serve and reverence dervishes; and that of the Junaydís is to keep watch over one’s spiritual state (_muráqaba-i báṭin_). Footnote 114: The followers of Ḥamdún al-Qaṣṣár, who are generally called Qaṣṣárís. The object of all austerities and acts of self-mortification is resistance to the lower soul (_nafs_), and until a man knows his lower soul his austerities are of no use to him. Now, therefore, I will explain the knowledge and true nature of the lower soul, and in the next place I will lay down the doctrine concerning self-mortification and its principles. _Discourse touching the true nature of the Lower Soul_ (nafs) _and the meaning of Passion_ (hawá).