Sahih Muslim Book 001, Hadith Number 0017.
Chapter : Concerning Iman by which a person would enter Heaven.
It is narrated on the authority of Jabir that a man once said to the Messenger of Allah (may peace be upon him): Shall I enter Paradise in case I say the obligatory prayers, observe the (fasts) of Ramadan and treat that as lawful which has been made permissible (by the Shari'ah) and deny myself that what is forbidden, and make no addition to it? He (the Holy Prophet) replied in the affirmative. He (the inquirer) said: By Allah, I would add nothing to it.