Sahih Muslim Book 34, Hadith Number 6448.
Chapter : Following the footsteps of the Jews and the Christians.
Abu Sa’id al-Khudri reported Allah’s Messenger (may peace be upon him) as saying: You would tread the same path as was trodden by those before you inch by inch and step by step so much so that if they had entered into the hole of the lizard, you would follow them in this also. We said: Allah’s Messenger, do you mean Jews and Christians (by your words) “those before you”? He said: Who else (than those two religious groups)?