Musannaf Ibn Abi Shayba 20:8

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Hisham ibn ‘Urwah, from his father, from al-Miswar: That ‘Umar consulted the people regarding the *imlas* (miscarriage caused by an assault) of a woman. Al-Mughirah ibn Shu’bah said: "I witnessed the Messenger of Allah, may Allah bless him and grant him peace, judge regarding it with a *ghurrah* (compensation) of a male slave or a female slave." ‘Umar said: "You must bring someone who will testify." So Muhammad ibn Maslamah testified for him.