Sayyiduna Ibn Abbas (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) asked Abu Dharr (may Allah be pleased with him): "Which of the handholds of faith is the firmest - I think he (peace and blessings be upon him) said this?" He said: Allah and His Messenger (peace and blessings be upon him) know best. He (peace and blessings be upon him) said: "Allying for the sake of Allah, showing enmity for the sake of Allah, loving for the sake of Allah, and hating for the sake of Allah."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11488