Sayyiduna Ali (may Allah be pleased with him) narrates: "We were sitting in the mosque with the Prophet (peace and blessings be upon him), waiting for the prayer, when a man stood up and said: 'I have committed a sin.'" The Prophet (peace and blessings be upon him) turned away from him. When he (peace and blessings be upon him) finished the prayer, the man stood up again and repeated the same words. Then the Prophet (peace and blessings be upon him) said: "Did you not pray this prayer with us and perform ablution well for it?" He said: "Yes, indeed." He (peace and blessings be upon him) said: "Then this prayer is an expiation for your sin."
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Abu Ishaq except Isra'il, and no one narrated it from Isra'il except Abd al-Rahman bin Yahya al-Madani; Ali bin Harb is alone in narrating it; and it is narrated from Sayyiduna Ali (may Allah be pleased with him) only with this chain."
Hadith Referenceالمعجم الأوسط / باب الميم / 7560
Hadith Gradingمحدثین:إسناده ضعيف لضعف الحارث
Hadith Takhrij«قال الهيثمي: فيه الحارث ضعيف «مجمع الزوائد ومنبع الفوائد، ج 1، ص 301»» «أخرجه الطبراني فى «الصغير» برقم: 915»