Abū Saʿīd Abū'l-Khayr or Abusa'id Abolkhayr () (December 7, 967 - January 12, 1049), also known as Sheikh Abusaeid or Abu Sa'eed, was a famous Persian Sufi and poet who contributed extensively to the evolution of Sufi tradition. The majority of what is known from his life comes from the book Asrar al-Tawhid (اسرارالتوحید, or "The Mysteries of Unification") written by Mohammad Ibn Monavvar, one of his grandsons, 130 years after his death. The book, which is an important early Sufi writing in Persian, presents a record of his life in the form of anecdotes from a variety of sources and contains a collection of his words. During his life his fame spread throughout the Islamic world, even to Spain. He was the first Sufi writer to widely use ordinary love poems as way to express and illuminate mysticism, and as such he played a major role in foundation of Persian Sufi poetry. He spent most of his life in Nishapur. Biography Abū-Sa'īd was born in the village of Mihne, part of Greater Khorasan, today located near mihne in Akhal Province. His father was a herbalist and physician with an interest in Sufism. He then moved and lived in the city of Nishapur, and subsequently moved back to Meyhaneh after a few years. Abū-Sa'īd's formal education included Islamic scholarship and Arabic literature that he continued until the age 23 when he left them for Sufism. He also traveled to and spent time in small towns around the same province visiting other Sufis or his teachers. He studied jurisprudence and hadith for many years in Marv and Sarakhs until, in an important event in his life, he abandoned his studies and joined the circle of Sufis and turned to the valley of mysticism. After receiving the method of Sufism from Sheikh Abolfazl Sarakhsi and Abul-Abbas Qassab Amoli, Sheikh Abu Said returned to his original country and practiced austerity for seven years and went to Nishabur at the age of 40. Mysticism His mysticism is a typical example of the Khorasani school of Sufism. He extracted the essence of the teachings of the past Sufis of this school (and to some extent other schools as well) and expressed them in a simpler, and in a sense deeper, form without the use of philosophy. He held a special reverence for earlier Sufis, especially Bayazid Bastami and Hallaj. Moreover, in Asrar al-Tawhid, Tazkiratul Awliyā