Chapter on Oaths, Vows, and Expiations
Man Lā Yaḥḍuruh al-Faqīh|Volume 3|Book 2|Chapter 38
وَ رَوَى حَفْصُ بْنُ عُمَرَ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ قَالَ: سُئِلَ رَسُولُ اَللَّهِ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ مَا كَفَّارَةُ اَلاِغْتِيَابِ قَالَ "تَسْتَغْفِرُ لِمَنِ اِغْتَبْتَهُ كَمَا ذَكَرْتَهُ ".
Hafs ibn Umar narrated from Abu Abdillah عليه السلام that the Messenger of Allah سبحانه وتعالى (peace be upon him and his family) was asked: "What is the expiation for backbiting?" Imam عليه السلام said: "You should seek forgiveness for the one you have backbitten, just as you mentioned him."
- Ṣaḥīḥ al-Faqīh