Sahih Bukhari Volume 008, Book 077, Hadith Number 595.
Narated By Imran bin Husain : A man said, "O Allah's Apostle! Can the people of Paradise be known (differentiated) from the people of the Fire; The Prophet replied, "Yes." The man said, "Why do people (try to) do (good) deeds?" The Prophet said, "Everyone will do the deeds for which he has been created to do or he will do those deeds which will be made easy for him to do." (i.e. everybody will find easy to do such deeds as will lead him to his destined place for which he has been created).