“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.
Bukhari 1:15 http://www.sacred-texts.com/isl/bukhari/bh1/bh1_14.htm
Sunni Hadith