Husayn (may Allah have mercy on him) said: I saw a man who was given the hadd punishment for slander on the basis of suspicion. When the punishment was finished, he repented. He said: "I seek forgiveness from Allah and repent to Him for slandering chaste women." The narrator said: I met Abu al-Zinad (may Allah have mercy on him) and told him about this, and he said: "With us, when he retracts his statement and repents, his testimony will be accepted."
(b) The Shaykh (may Allah have mercy on him) said: Abdullah bin Utbah (may Allah have mercy on him) has a saying concerning the testimony of the slanderer.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20555