In the beginning of the Book of Tafsir, in his Sahih, Al-Bukhari 
said; "It is called Umm Al-Kitab, because the Qur'an starts with it and 
because the prayer is started by reciting it.'' It was also said that it
 is called Umm Al-Kitab, because it contains the meanings of the entire 
Qur'an. Ibn Jarir said, "The Arabs call every comprehensive matter that 
contains several specific areas an Umm. For instance, they call the skin
 that surrounds the brain, Umm Ar-Ra's. They also call the flag that 
gathers the ranks of the army an Umm.'' He also said, "Makkah was called
 Umm Al-Qura, (the Mother of the Villages) because it is the grandest 
and the leader of all villages. It was also said that the earth was made
 starting from Makkah.'' 
 Further, Imam Ahmad recorded that Abu Hurayrah narrated about Umm Al-Qur'an that the Prophet said, 
  
 
 The Reason it is called Umm Al-Kitab 
 In the beginning of the
 Book of Tafsir, in his Sahih, Al-Bukhari said; "It is called Umm 
Al-Kitab, because the Qur'an starts with it and because the prayer is 
started by reciting it.'' It was also said that it is called Umm 
Al-Kitab, because it contains the meanings of the entire Qur'an. Ibn 
Jarir said, "The Arabs call every comprehensive matter that contains 
several specific areas an Umm. For instance, they call the skin that 
surrounds the brain, Umm Ar-Ra's. They also call the flag that gathers 
the ranks of the army an Umm.'' He also said, "Makkah was called Umm 
Al-Qura, (the Mother of the Villages) because it is the grandest and the
 leader of all villages. It was also said that the earth was made 
starting from Makkah.'' 
 Further, Imam Ahmad recorded that Abu Hurayrah narrated about Umm Al-Qur'an that the Prophet said,