عن أبي الدرداء رضي الله عنه عن النبي صلى الله عليه وسلم قال:
«مَنْ رَدَّ عَنْ عِرْضِ أَخِيهِ رَدَّ اللهُ عَنْ وَجْهِهِ النَّارَ يَوْمَ الْقِيَامَةِ».  
                        
[صحيح] - [رواه الترمذي وأحمد] - [سنن الترمذي: 1931]
                        
 المزيــد ... 
                    
Abu ad-Dardā’ (may Allah be pleased with him) reported: The Prophet (may Allah’s peace and blessings be upon him) said:
"Whoever protects the honor of his brother in his absence, Allah will protect his face from the Fire on the Day of Judgment." 
                                                     
                                                                                                    
[Authentic hadith] - [Narrated by At-Termedhy & Ahmad] - [Sunan At-Termedhy - 1931]                                            
The Prophet (may Allah's peace and blessings be upon him) informs that if a Muslim defends the honour of his fellow Muslim in his absence by preventing others from backbiting him, Allah will protect him from the punishment on the Day of Judgment.