Musnad Abu Ya'la al-Mawsili 116:42

Ahmad narrated to us, Abu Dawud narrated to us, he said: Shu'bah informed us, from Qatadah, Anas ibn Malik narrated to us, he said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Three things, whoever possesses them will find the sweetness of faith through them: That Allah and His Messenger are more beloved to him than anything else besides them; and that being cast into the Fire is more beloved to him than returning to disbelief after Allah has saved him from it; and that a person loves another, not loving him except for the sake of Allah."