Sahih Muslim Book 1, Hadith Number 14.

Chapter : Concerning Iman by which a person would enter Heaven.

It is reported on the authority of Abu Huraira that a bedouin came to the Messenger of Allah (may peace be upon him) and said: Messenger of Allah, direct me to a deed by which I may be entitled to enter Paradise. Upon this he (the Holy Prophet) remarked: You worship Allah and never associate anything with Him, establish the obligatory prayer, and pay the Zakat which is incumbent upon you, and observe the fast of Ramadan. He (the bedouin) said: By Him in Whose hand is my life, I will never add anything to it, nor will I diminish anything from it. When he (the bedouin) turned his back, the Prophet (may peace be upon him) said: He who is pleased to see a man from the dwellers of Paradise should catch a glimpse of him.