It is narrated from Sayyiduna Mu'adh bin Anas al-Juhani (may Allah be pleased with him) that he asked the Messenger of Allah (peace and blessings be upon him) about the most excellent faith. He (peace and blessings be upon him) said: "The most excellent faith is that you love for the sake of Allah, hate for the sake of Allah, and employ your tongue in the remembrance of Allah." He said: And what else, O Messenger of Allah? He (peace and blessings be upon him) said: "And that you love for people what you love for yourself, dislike for them what you dislike for yourself, and that you speak good or remain silent."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17560