Hadithcore
Riyad as-Salihin, 1530

Ka'b bin Malik (May Allah be pleased with him) said in his long story about his repentance:

The Prophet (ﷺ) was sitting among the people in Tabuk. He (ﷺ) said, "What happened to Ka'b bin Malik?" A person from the tribe of Banu Salamah said: "O Messenger of Allah! the embellishment of his cloak and an appreciation of his sides have allured him, and he was thus detained." Mu'adh bin Jabal (May Allah be pleased with him) said: "Woe be upon you! You have passed indecent remarks. O Messenger of Allah! by Allah, we know nothing about him but good." The Messenger of Allah (ﷺ) remained silent. <b>[Al- Bukhari and Muslim]</b>.

وعن كعب بن مالك رضي الله عنه في حديثه الطويل في قصة توبته وقد سبق في بابه التوبة‏.‏ قال‏:‏ قال النبي صلى الله عليه وسلم وهو جالس في القوم بتبوك‏:‏ ‏"‏ما فعل كعب مالك‏؟‏ فقال رجل من بني سلمة‏:‏ يا رسول الله حبسه برداه، والنظر في عطفيه فقال معاذ بن جبل رضي الله عنه بئس ما قلت والله يا رسول الله ما علمنا عليه إلا خيرًا، فسكت رسول الله صلى الله عليه وسلم‏"‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏‏.‏ "عِطْفَاهُ"جانِباهُ، وهو إشارةٌ إلى إعجابِهِ بنفسهِ.

References1 variant
In-Book Reference
Book 17, Hadith 20
Sharh · explanationclick to expand
<b>Guidance from the Hadith:</b><br> 1) Whoever hears his Muslim brother being backbitten must defend him and express his disapproval to the backbiter. This is one of the rights the believers have upon one another.<br> 2) Attending gatherings where there is backbiting of others, and assaulting the honors of people without showing one’s disapproval of that exposes him to punishment.