The Book on Government (Kitab Al-Imara)
Muslim :: Book 20 : Hadith 4609
It has been narrated on the authority of Ibn 'Umar that the Messenger of Allah (may peace be upon him) said: Do not take the Qur'an on a journey with you, for I am afraid lost it should fall into the hands of the enemy. Ayyub (one of the narrators in the chain of transmitters) said: The enemy may seize it and may quarrel with you over it.