Some of the earliest works studying the Arabic language were started in the name of Islam. Tradition has it that the caliph Ali, after reading a copy of the Qur'an with errors in it, asked Abu al-Aswad al-Du'ali to write a work codifying Arabic grammar. Khalil ibn Ahmad would later write "Kitab al-Ayn", the first dictionary of Arabic, along with works on prosody and music, and his pupil Sibawayh would produce the most respected work of Arabic grammar known simply as "al-Kitab" or "The Book".