Sahih_Bukhari

Volume 1, Book 2, Number 15:

Narrated 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."