Ali bin Husayn (may Allah have mercy on him) narrates from his father, Sayyiduna Husayn bin Ali (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "Part of the excellence of a person's Islam is his leaving what does not concern him."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2873