Musannaf Ibn Abi Shayba 19:312

Abu Bakr narrated to us, he said: 'Abdah bin Sulayman narrated to us, from Yahya bin Sa'id, from Sulayman bin Yasar, from Ibn Abi Rabi'ah, who said: 'Umar invited us, among some young men of the youth of Quraysh, regarding some slave women who were accused of immorality from the slaves of the government. So we struck them fifty [lashes] each, fifty [lashes] each.'