It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that a man said: "O Messenger of Allah! Who is a Muslim?" He (peace and blessings be upon him) said: "A Muslim is the one from (the harm of) whose tongue the Muslims are safe."
Imam al-Tabarani (may Allah have mercy on him) said: "These hadiths are narrated from Abu Umamah (may Allah be pleased with him) only with this chain; Faddal is alone in narrating them."
Hadith Referenceالمعجم الأوسط / باب الألف / 2543
Hadith Takhrij«أخرجه الطبراني فى «الكبير» برقم: 8021»