صحيح البخاري

Narrated Abu Juhaifa:

I asked `Ali, "Do you have the knowledge of any Divine Inspiration besides what is in Allah's Book?" `Ali replied, "No, by Him Who splits the grain of corn and creates the soul. I don't think we have such knowledge, but we have the ability of understanding which Allah may endow a person with, so that he may understand the Qur'an, and we have what is written in this paper as well." I asked, "What is written in this paper?" He replied, "(The regulations of) blood-money, the freeing of captives, and the judgment that no Muslim should be killed for killing an infidel."