Sahl al-Tustari

Abu Muhammad Sahl Bin Abdullah Al Tustari (818-896) was an early scholar of Islam an notable commentator on Sufism. He was born in the fortress town of Tustar (Arabic) or Shushtar (Persian) in what is now southwestern Iran.

It is said that Sahl would often wake up in the middle of the night only to see his devout uncle carrying out his prayers. He asked his uncle if he could be like him, to which his uncle, Muhammad ibn al-Sawwar replied, "You are still young, suffice that every night you remember Allah in your heart by repeating these words 3 times without moving your tongue. When you are strengthened by it, increase it to 7 times. This will be benificial for you for if you know Allah is witnessing you, Allah is looking at you and Allah is with you, surely you will not do anything that would displease Him."

So say:"Allahu shahidi, Allahu naziri, Allahu ma'i" (Allah is watching me. Allah is looking at me. Allah is with me.)
This was to become his lifelong practice till he was named by al-Dhahbi as "the master of the knowers" (Shaykh al-'arifin). Al-Qushayri said of him, "He had no peer in his time for correctness of transaction and superlative God consiousness (taqwa), and he was a person given to charismatic actions (karamat)".

Tustari's teacher for a time was Dhun Nun al-Misri, and he was himself the teacher of Mansur al-Hallaj for a time.
Tustari wrote a comprehensive commentary of the Quran. He maintained the the Quran "contained several levels of meaning", which included the outer (zahir) and the inner (batin) levels.  Another key idea that he unravelled was the meaning of the Prohet Muhammad's saying "I am He and He is I, save that I am I, and He is He", explaining it "as a mystery of union and realization at the center of the Saint's personality, called the sirr ('the secret'), or the heart, where existence joins Being."

Tustari also was the first to put forward the Sufi exercise of remembrance of God, Dhikr, on a firm theoretical basis with evidence from the Quran and Sunnah.

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