Sayyiduna al-Nawwas bin Sam'an (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "It is a great betrayal that you tell your brother something about which he believes you to be truthful, while you are lying."
Imam Ahmad recorded this narration from his teacher Umar bin Harun, whom Qutaybah and others declared thiqah (trustworthy), while Yahya bin Ma'in and others called him da'if (weak). The remaining narrators of this narration are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب العلم / 612
Hadith Gradingمحدثین:إسنادہ ضعیف
Hadith Takhrij«أورده المؤلف فى زوائد المسند 128 ، أخرجه مسند أحمد برقم: 17183»