Sahih Bukhari Volume 3, Book 48, Hadith Number 850.

Narated By Ubaidullah bin Abdullah bin Utba : Ibn Abbas said, “O Muslims? How do you ask the people of the Scriptures, though your Book (i.e. the Quran) which was revealed to His Prophet is the most recent information from Allah and you recite it, the Book that has not been distorted? Allah has revealed to you that the people of the scriptures have changed with their own hands what was revealed to them and they have said (as regards their changed Scriptures): This is from Allah, in order to get some worldly benefit thereby.” Ibn Abbas added: “Isn’t the knowledge revealed to you sufficient to prevent you from asking them? By Allah I have never seen any one of them asking (Muslims) about what has been revealed to you.”