Sahih Bukhari Volume 001, Book 002, Hadith Number 015.

Narated By Anas : The Prophet said, "Whoever possesses the following three qualities will have the sweetness (delight) of faith:

1. The one to whom Allah and His Apostle 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."