It is narrated from Sufyan bin ‘Uyaynah (may Allah have mercy on him) that I heard Zuhri (may Allah have mercy on him) saying that the people of Iraq believe that the testimony of a qadhif (one who falsely accuses someone of adultery) is not permissible, and I bear witness that Sa‘id bin al-Musayyib (may Allah have mercy on him) informed me that Sayyiduna ‘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 he said: “If you repent, I will accept your testimony.” Imam Shafi‘i (may Allah have mercy on him) says that Sufyan bin ‘Uyaynah (may Allah have mercy on him) used to narrate it in this way several times, then once he said that he became doubtful about it. Imam Shafi‘i (may Allah have mercy on him) says that Sufyan (may Allah have mercy on him) said: I bear witness that so-and-so informed me (then he also mentioned the name, but I could not remember the name of that narrator), so I inquired about it, and my classmate ‘Amr bin Qays (may Allah have mercy on him) told me that it was Sa‘id bin al-Musayyib (may Allah have mercy on him), so Sufyan (may Allah have mercy on him) (after that) did not doubt the name of Sa‘id bin al-Musayyib (may Allah have mercy on him).
Hadith Referenceالسنن المأثورة / باب تفسير الفرعة والعتيرة / 409
Hadith Takhrijالمعجم الكبير للطبراني: 373,372/7 ، التلخيص الجير: 208/4، معاني الآثار للطحاوي: 153/4