The Book of Faith (Kitab Al-Iman)
Muslim :: Book 1 : Hadith 67
It is reported on the authority of Anas that the Prophet of Allah (may peace and blessings be upon him ) said: There are three qualities for which anyone who is characterised by them will relish the sweetness of faith: he to whom Allah and His Messenger are dearer than all else; he who loves a man for Allah's sake alone; and he who has as great an abhorrence of returning to unbelief after Allah has rescued him from it as he has of being cast into Hell.