It is reported on the authority of Abu Huraira that a bedouin came to the Messenger of Allah (SAW) 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 (SAW) said: He who is pleased to see a man from the dwellers of Paradise should catch a glimpse of him.
Reference : Sahih Muslim 14 b
In-book reference : Book 1, Hadith 15
USC-MSA web (English) reference : Book 1, Hadith 14
(deprecated numbering scheme)