Abu Sa'id Abu'l-Khayr, Fazlullah ibn Ahmad ibn Muhamamd ibn Ibrahim Mayhani (967-1048), a well-known Ash'ari Sufi, poet, and mystic from Khurasan, reportedly from Mayhana, a well-known village in the district of Khawaran, located between Sarakhs and Abiward. He was also known as Fazl which is recorded as Fuzayl in some sources. Historians have unanimously recorded the name of his father, though those who recorded his father's name as Muhammad have ignored one degree of his line of descent. However, discrepancies exist as to the names of his grandfather and great grandfather. His grandfather and his great grandfather have been recorded as 'Ali and Ahmad respectively. Abu Sa'id was born to a Shafi'i family in Mayhana. His father, a pious man, was an apothecary and he was called by the inhabitants of Mayhana as Babu Abu al-Khayr. He was a man of substance and socialized with the Sufis of the city. He was first introduced to Sufism through his father. One night, as a child and at his mother's insistence, he accompanied his father participating a Sufi gathering and was acquainted with the Sufi etiquette of Sama and even committed to memory a song recurrently sung by a vocalist, although he could not make out its mystical meaning. His mystical intuitive faculty was influenced by his father's friendly ties to some Sufi masters, e.g. Abu al-Qasim Bishr Yasin. He learned to recite the Qur'an from Abu Muhammad 'Annazi and at his father's suggestion he began studying philology and literature with Abu Sa'id 'Annazi, the mufti and belletrist of renown. He met with Bishr Yasin at times and such meetings grest attraction for him. He learned the basics of Sufism in his childhood and adolescence from Bishr Yasin. Abu Sa'id lived in Mayhana when he was at least 17 years of age and visited Bishr Yasin's tomb after the latter's death in 990. In Mayhana, Abu Sa'id learned religious and mystical teachings and had gone so far in studying Arabic literature that he had committed to memory more than 30,000 couplets of pre-Islamic Arabic poetry. Then, he departed from his hometown for Marv to learn Islamic law. He first studied Shafi'i principles of law and comparative law with Abu 'Abdullah Khizri for five years. His master was well acquainted with the Sufi path and Abu Sa'id learned mysticism from him. After his master's death, he furthered his legal studies at the teaching circles held by Abu Bakr Qaffal Marvazi, a well-known expert in Islamic law in that city. His classmates included some if the renowned traditionists (muhadis) and jurisprudants of the time, e.g. Abu Muhammad Juwaini, Abu 'Ali Sanji, and Nasir Marvazi. Abu Sa'id were his cassmates at the lesons of these great by muhadis at Marv. He departed for Sarakhs at the age of 30 to attend the classes of Abu 'Ali Ahmad Zahir, an jurisprudant with whom he studied Qur'anic exegesis, principles of Islamic law, and traditions. When the renowned jurisprudent of Sarakhs discovered his remarkable faculty, he taught him what he usually taught in three days in just one day. However, mystically inclined from a young age Abu Sa'id who had been acquainted with mystical teachings of great masters, e.g. Abu al-Qasim Bishr Yasin, and the mystical milieu of Sarakhs, in which spiritual masters like Luqman and Abu al-Fazl Sarakhsi were active, made him turn away from Islamic Law and scholastic indevors and to quit the lessions held by the jurisprudent of Sarakhs to join a Sufi center headed by a mystic of Sarakhs Abu al-Fazl Sarakhsi. Next to Bishr Yasin Sarakhsi Sarakhsi was to have the greates influence on Abu Said even more so than Qassab Amuli. Abu Sa'id addressed Abu al-Fazl as Pir (spiritual guide) and regarded pilgrimage to his tomb on a par with that to Mecca.
By the time he was forty he training and journey on the Sufi path. Therefore, it id doubtful he spemt long in the Khaniqa of Sarakhsi, since after the change he experienced after the recitation of the divine attribute "glorious majesty" in the presence of Abu al-Fazl, he returned to Mayhana at the latter's suggestion and lead the life of a recluse at his father's home, repeated divine names after the fashion of his spiritual guide from Sarakhs, and engaged himself in reclusive self-mortification, and at times frequented the deserts and the ruined caravansaries of Mayhana. It was at this time that he reflected on Sufi instructions and whenever he came to some matter unfamiliar to him, he traveled to Sarakhs and inquired it of Abu al-Fazl, at whose suggestion, he traveled to Nayshabur and was granted the Sufi robe from Abu 'Abd al-Rahman Sulami. After his parents' death, he still frequented the deserts in Mayhana, Bavard, Marv, and Sarakhs and devoted seven years to treading the Sufi path in seclusion engaged with self-mortification. After Abu al-Fazl's death at the end of the tenth century, Abu Sa'id departed from his hometown for Amul to visit Abu al-'Abbas Qassab Amuli, the third Shaykh who made remarkable contributions to Abu Sa'id's spiritual life, such that Abu Sa'id called him the perfect "Shaykh" and uttered what he heard and learned from him to his last days. Abu Sa'id left his hometown for Nayshabur in early 11th century, but on his way to Nayshabur, he visited Muhammad Ma'shuq Tusi in Tus and stayed for a while at the Sufi centre headed by Abu Ahmad where he seemingly conversed with Abu al-Qasim Kurrakani. The day after his arrival, Abu Sa'id lectured at the Sufi center of Tartusi and thus quickly made a name for himself in the city and numerous disciples residing at other Sufi centers were eager to attend his lectures, such that the disciples of a religious Shaykh like Abu al-Qasim Qushayri regarded it an opportunity to attend his lectures, though Qushayri forbade them from their attendance. Finally, Qushayri's disciples insisted on taking him to Abu Sa'id's circle. When Qushayri perceived his ability to read his mind, he desisted from denying him. Besides Qushayri, Abu 'Ali Bakuya disfavored Abu Sa'id's Sufi etiquette in Nayshabur and denied him. Khwaja 'Abdullah Ansari, despite his firm belief in Hanbali principles was not in line with Abu Sa'id's teachings, traveled to Nayshabur two times and met with Abu Sa'id. Abu Sa'id lived in this manner in Nayshabur for ten years, but one day, while performing spiritual dance, his son, Abu Sa'id Tahir asked for permission to go on pilgrimage to Mecca. Abu Sa'id intended to accompany him, despite the insistence of the disciples and spiritual masters of the city against such intention. Nonetheless, Abu Sa'id left the city for Mecca, but when he approached Kharaqan, Abu al-Hasan Kharaqani invited him to the city and sent his son, Ahmad, and some of his disciples to welcome him. Abu Sa'id stayed there for three days and as suggested by the Sufi master of Kharaqan, he changed his course from Hijaz to Nayshabur through Bastam. He resided in Bastam for one day to visit the tomb of Bayazid. Then he traveled to Damghan through Bastam and in his return from Damghan, he traveled again to Kharaqan through Bastam. Once again, Kharaqani dispatched some disciples to invite him to his Sufi center. Abu Sa'id stayed in Kharaqan for three days and being seen off by Abul al-Hasan's disciples, he departed for Nayshabur through Jajarm. He stayed some more years in Nayshabur and held his last circle on 5 January 1049 where he appointed Abu Tahir Sa'id as his successor and provided his disciples with instructions as to his burial. He lived for another week and died on 12 January of that year at an age exceeding 83. His body was buried at his home the day after.
He spent most of his life in Nayshabur and also lived some part of his life in his hometown, Mayhana, and except for some journeys made to regions in the vicinity of Mayhana and Nayshabur, he never made long journeys. His most significant journeys were seemingly to Amul to meet Abu al-'Abbas Qassab, to Kharaqan to see Kharaqani, and to Qumis. He studied traditions with Abu 'Ali Shabubi and Abu Bakr Jawzaqi. Abu Sa'id issued licenses for transmission of traditions to numerous traditionists and Sufis. Hasan Samarqandi attended his sessions and Abu Bakr Nassaj, Abu 'Ali Farmadi, and Bashkhwani were among his disciples. Numerous poems, compiled in a collection entitled Ruba'iyyat-i Abu Sa'id, have been attributed to Abu Sa'id. One of the most remarkable events in the history of Sufism in general and Abu Sa'id's life in particular, is his correspondence, and as reported by some historians his meeting, with Ibn Sina. In Abu Sa'id's biographical account entitled Asrar al-Tawhid, Muhammad ibn Munawwar records the earliest account of this meeting including parts of the correspondence exchanged between the two figures. Abu Sa'id's spiritual heritage mainly lies in his mystical teachings, though he is well-known in the cultural history of Persia, on a par with Baba Tahir, Khayyam, Rumi, and 'Attar. He never composed poetry and what he uttered had been the poetry of his master, Abu al-Qasim Bishr Yasin, collected by the descendants of the former. Although Abu Sa'id was a distinguished scholar well-versed in the sciences of his time, e.g. Qur'anic exegesis, traditions, Islamic law, and belles-lettres, he refrained from authoring any works, though some of his correspondence, dictations, and words have survived. His extant lines of poetry include a quatrain and a single couplet, acknowledged by Muhammad Munawwar and Mahmud Ghujdawani to be his compositions; nonetheless, the quatrains attributed to him are mainly by others. His words, suggestions, and instructions are recognized as his own and attribution of some of them to him is indubitable. A work entitled Dhikr Sultan Abi Sa'id whose manuscript copy is dated 1472 is seemingly one of such attributed works. However, one of the dictations of him is a chapter on Sufi etiquette, as explicitly mentioned by Muhammad ibn Munawwar, was dictated by the spiritual guide of Mayhana, viz. Abu Sa'id, and written down by Abu Bakr Mu'addib, the text of which has been incorporated in Muhammad ibn Munawwar's compilation. His extant compositions include his correspondence addressed to the offspring of Sufi masters and his contemporaneous notables. Another work attributed to him is Maqamat-i Arba'in, regarded by modern day scholars as a later composition. The sources treating of him include Halat va Sukhanan-i Abu Sa'id by Abu Ruh Lutfullah ibn Sa'd ibn As'ad ibn Abi Tahir Sa'id ibn Abi Sa'id Fazlullah Mayhani and Asrar al-Tawhid fi Maqamat al-Shaykh Abi Sa'id by Muhammad ibn Munawwar ibn Abi Sa'id ibn Abi Tahir Sa'id ibn Abid Sa'id Mayhani.
Asar-afarinan (1, 166); Tarikh-i Adabiyyat dar Iran (1, 603-606, 2, 978-979); Tadhkirat al-Awliya' (2, 322-337); Da'irat al-Ma'arif-i Farsi (1, 35); Nafahat al-Uns (305-312).