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 in which he considers you truthful, while you are lying to him."
This narration was recorded by Imam Ahmad and Imam al-Tabarani. Its chain contains a narrator, Umar bin Harun, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدب / 13170
Hadith Gradingمحدثین:إسنادہ ضعیف
Hadith Takhrij«اخرجه احمد فى المسند (183/4) ، أخرجه مسند أحمد برقم: 17183»