Sufyan bin ‘Uyaynah (may Allah have mercy on him) narrated that I heard al-Zuhri (may Allah have mercy on him) say: The people of Iraq think that the testimony of one who accuses others (of adultery) is not permissible. And I bear witness that Sa‘id bin al-Musayyib (may Allah have mercy on him) informed me that ‘Umar bin al-Khattab (may Allah be pleased with him) said to Abu Bakrah (may Allah be pleased with him): “Repent, and your testimony will be accepted, or if you repent, your testimony will be accepted.” Imam al-Shafi‘i (may Allah have mercy on him) said: I heard Sufyan bin ‘Uyaynah (may Allah have mercy on him) narrate it several times in this way, then I heard him say that he had some doubt about it. Imam al-Shafi‘i (may Allah have mercy on him) said: I bear witness that so-and-so informed me—then he mentioned a man whose name I could not remember, so I asked him, and ‘Umar bin Qays informed me that he narrates from Sa‘id bin al-Musayyib. And Sufyan (may Allah have mercy on him) did not have any doubt regarding Sa‘id bin al-Musayyib. Imam al-Shafi‘i (may Allah have mercy on him) said: And besides him, no one else narrates it from Ibn Shihab except Sa‘id bin al-Musayyib (may Allah have mercy on him), and he narrates from ‘Umar (may Allah be pleased with him).
Hadith Referenceمسند الإمام الشافعي / كتاب القضاء والأحكام والدعاوى والبينات واليمين ومع الشاهد والأيمان والشهادات / 1703
Hadith Takhrijاسناده صحيح اخرجه البيهقي : 10 / 152 - وفى المعرفة السنن والآثار له (5891) وابن ابي شيبة (20648) - والطبري في تفسيره : (76/18)۔
Sufyan bin ‘Uyaynah informed us, he said: Zuhri informed me. Then when we stood up (from the gathering), ‘Umar bin Qais, who was present with me in the gathering, said to me that he is Sa‘id bin al-Musayyib. I asked Sufyan (may Allah have mercy on him): “Did you have doubt when Sa‘id bin al-Musayyib (may Allah have mercy on him) informed you?” He replied: “No, it is exactly as he said, but he made me doubtful.”
Hadith Referenceمسند الإمام الشافعي / كتاب القضاء والأحكام والدعاوى والبينات واليمين ومع الشاهد والأيمان والشهادات / 1704
Hadith Takhrijاسناده صحيح : أخرجه البيهقي : 10 / 152 - وفى المعرفة السنن والآثار له (5891)۔
It is narrated from Sa'id bin al-Musayyib (may Allah have mercy on him) that when 'Umar bin al-Khattab (may Allah be pleased with him) enforced the hadd of qadhf on three men, he made them repent. Two of them repented, so he accepted their testimony, but Abu Bakrah (may Allah be pleased with him) refused to repent, so his testimony was also rejected.
Hadith Referenceمسند الإمام الشافعي / كتاب القضاء والأحكام والدعاوى والبينات واليمين ومع الشاهد والأيمان والشهادات / 1705
Hadith Takhrijاسناده ضعيف لابهام شيخ الشافعي : اخرجه البيهقي : 10 152 - وفى المعرفة السنن والآثار له (5892)۔