The Sunnah Way of the Sufis (Risala al-Mustarshidin) - Imam Harith al-Muhasibi (RA)
Revised and explained by Shaikh Abdul Fattah Abu Ghuddah (RA)
' Whoever carefully examines the branches of knowledge will find that none of them are beyond the pale of the Shariah. The True Sufi' agree that 'This knowledge of ours is built on the Qur'an and The Sunnah.'