Sayyidah Asma bint Yazid (may Allah be pleased with her) narrates: The Prophet (peace and blessings be upon him) said: "Whoever defends the honour of his brother against backbiting, it is binding upon Allah Almighty to free him from the Fire."
This narration was recorded by Imam Ahmad and Imam al-Tabarani, and Imam Ahmad's chain is hasan (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدب / 13150
Hadith Gradingمحدثین:إسنادہ حسن۔
Hadith Takhrij«أخرجه مسند أحمد برقم: 27062، 27063»