"ʿAṭṭār’s only prose work; it is a collection of biographies dedicated to exponents and pioneers of classical Sufism, beginning with Imam Jaʿfar al-Ṣādeq, Oways Qaranī, and Ḥasan Baṣrī, and ending with Ḥallāj, whom ʿAṭṭār evidently felt to be the perfector of Sufism. The biographies of later Sufis, including ʿAṭṭār’s favorite mentor Abū Saʿīd b. Abi’l-Ḵayr, are not from his own pen. The work gives a sort of hagiographic summary of his career in the ethical and experiential world of the Sufis (see above). It is to be regretted that he hardly ever names his sources. He appears to have relied almost entirely, if not exclusively, on written sources. In his choice and narration of edifying and memorable stories, he shows a distinctive taste of his own. Comparisons with versions of the same material in works by other authors suggest that he presented and interpreted the stories somewhat idiosyncratically (Ritter, “Philologika XIV,” p. 63). On the other hand, he translated sayings of his Sufis, which had come down in Arabic, very faithfully into Persian. The work has also interested Iranian scholars as a specimen of early Persian prose (G. Lazard, La Langue des plus anciens monuments de la prose persane, Paris, 1963, p. 121)." from http://www.iranicaonline.org/articles/attar-farid-al-din-poet