Sayyiduna Iyad bin Himar (may Allah be pleased with him) asked the Prophet (peace and blessings be upon him), saying: O Prophet of Allah (peace and blessings be upon him)! What is your view of a man who reviles me while he is inferior to me in lineage? He (peace and blessings be upon him) said: "Two people who revile each other are devils who rail and lie against each other."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 21088