For many centuries the epistle on Sufism by al-Qushayri (986 – 1072) has been the most popular reference book on Sufi ideology. Al-Qushayri’s epistle had a substantial impact not only on the formation of ideology of various Sufi schools but also on the development of Persian Sufi literature. Some of al-Qushayri’s ideas and morality tales are found in the poems of the outstanding Persian Sufi poet Farid al-Din ‘Attar (died between 1220 and 1234). Despite the restrained scientific description of mystical theories, al-Qushayri's stories have been represented in the imagery of Persian Sufi poetry and literature.