According to the Sufi master Abū Ibrāhīm Ismāʿīl b. Muḥammad Mustamlī Bukhārī (d. 1042), the sciences of the Sufis are the sciences of mystical states (aḥwāl), and these states are fruits produced by spiritual practices or works (aʿmāl). Also, according to Shaykh al-Akbar Ibn ʿArabī, true knowledge must be united with good works.