The Bala sar Mosque is the first mosque and place of worship which was built in the west of the Razavi Mausoleum following the martyrdom of Imam Reza (A.S.). The Bala sar Mosque is likely the same mosque that Moqadasi considered the best mosque in Khorasan. Because of large and magnificent mosques in Nughan, Tabaran, and Nishapur in Khorasan, the proximity of the Bala sar Mosque to the Imam Reza's Holy Mausoleum, and the virtue of praying in this mosque may have led Moqadasi to consider the Bala sar Mosque as the best mosque in Khorasan.
 Although determining the construction date of the Bala sar Mosque would greatly help in understanding the emergence and evolution of the Holy Razavi Shrine's architectural complex, the exact construction date of this mosque has not yet been clearly identified and explained.
In an incorrect reading of the Tarikh-e Bayhaqi (Bayhaqi's History), the founder of this small mosque has been stated as Abu al-Hasan Iraqi, the secretary of Sultan Masoud Ghaznavi (r. 1030-1042). Moreover, the burial of Iraqi in the Bala sar Mosque has strengthened this claim. This article, in an attempt to provide a suitable answer to clarify the construction date and founder of the Bala sar Mosque, has tried to examine the issue of attributing the construction of the Bala sar Mosque to Abu al-Hasan Iraqi by presenting historical evidence and referring to the fifth century AH endowed Qur'ans to the Astan Quds Razavi. Finally, this article tries to prove that, as Moqadasi stated, this mosque was built by A'mid al-Duwlah Fa'iq during the Samanid period.