Malik related to me from Abu'z-Zinad that he said, ''Umar ibn Abdal-Aziz flogged a slave with eighty lashes for slander."Abu'z-Zinad said, "I asked Abdullah ibn Amir ibn Rabia about that. Hesaid, 'I saw Umar ibn al-Khattab, Uthman ibn Affan, the Khalifs, andso on, and I did not see any of them flog a slave more than fortylashes for slander.' "
USC-MSA web (English) reference: Book 41, Hadith 17
Arabic reference: Book 41, Hadith 1519