Narrated Anas: The Prophet (peace be upon him) said, “Whoever possesses the following three qualities will have the sweetness (delight) of faith: 1. The one to whom Allah and His Apostle (peace be upon him) becomes dearer than anything else. 2. Who loves a person and he loves him only for Allah’s sake. 3. Who hates to revert to Atheism (disbelief) as he hates to be thrown into the fire.”
Sahih al-Bukhari, Vol. 1, Book 2, Hadith 9