 Al Majmu, a treatise written by the 13th century Arab scholar Muhyi ad-Din Yahya al-Nawawi, shows the founders of various Islamic schools of jurisprudence, including Imam Shafi and Imam Ahmad bin Hanbal, respectively from the eighth and ninth centuries, to have expressed different opinions on the issue.Shafi put his entire trust in arithmetic and astronomical calculations; Hanbal deemed the physical sighting of the moon mandatory, although he did not see local sighting as necessary — once the moon is sighted anywhere in the Muslim world, every follower of the faith must accept that.Ibn-e-Taymiyya, another 13th-century scholar, writing in his Risala fi’l-Hilal (Tract on the Crescent), “...categorically rejects the use of astronomical calculation in determining the lunar month.” Yaqut ibn Abdullah al-Hamawi, a 12th-century Arab biographer and geographer of Greek origin, gives the government complete authority in making such decisions.