Abū al-Dardāʾ (رضى الله عنه) narrated that the Messenger of Allāh (صلى الله عليه وسلم) said: “Whoever defends his brother’s honor in his absence, Allāh will protect his face from the Fire of Hell on the Day of Resurrection.”1
If he happens to attend a gathering and his Muslim brother is being mentioned with sin or being degraded, then he defends him as he would defend his own honour, because his brother’s honour is like his own.
“Whoever defends his brother’s honor in his absence…”
Meaning: In the state of his brother’s absence. If he happens to attend a gathering and his Muslim brother is being mentioned with sin or being degraded, then he defends him as he would defend his own honor, because his brother’s honor is like his own. Therefore he defends his brother’s honor, by censuring the backbiters and preventing them from persisting as it relates to the honor of his Muslim brother. He does not resign and stay quiet, leaving them to backbite. This is the Muslim’s obligation, and it is not permitted for him to stay quiet and keep the peace, for he will be sinning due to that and he will be a sharer and partner to them regarding the sin, (that is) because he saw an evil (taking place) and he did not change it, whilst having the ability to do so. How much more then, if he participated with them in the act, and he began backbiting with them? This is even worse. As for if he defends his brother’s honor and he prevents them from backbiting his brother, then Allāh, the Majestic and Exalted, will reward him by protecting his face from the Fire on the Day of Resurrection. This is a tremendous favor, because on the Day of Resurrection, the Fire will be brought in to view. He, the Most High, said:
وَبُرِّزَتِ الْجَحِيمُ لِمَن يَرَىٰ ﴿٣٦﴾
“And Hell-fire shall be made apparent in full view for (every) one who sees.”
And He, the Majestic and Exalted, said:
وَرَأَى الْمُجْرِمُونَ النَّارَ فَظَنُّوا أَنَّهُم مُّوَاقِعُوهَا ﴿٥٣﴾
“And the Mujrimūn (criminals, polytheists, sinners) shall see the Fire and apprehend that they have to fall therein.”
It will be hot and blazing, and nothing will protect against it except for righteous actions. A person will look to his right side, and he will not see anything except what he has done, and he will look to his left side and he will not see anything except what he has done, and he will look in front of himself and he will not see anything except the Fire; therefore, it is upon him to prepare for this situation. And from preparing for this situation is to refrain from (encroaching upon) the honor of the Muslim and defending them.
So this (ḥadīth) contains the exhortation toward defending the honor of the Muslims which is being violated in gatherings or in writings. If you were to see someone writing about a Muslim, and the ʿUlamāʾ specifically, and the Muslim Ruler, then it is upon you to defend them, as this is from defending the honor of the Muslims.