From Sahih Muslim (Hadith 4397):
Miswar b. Makhrama reported that 'Umar b. Khattab consulted people about the diyat of abortion of an unboam child. Mughira b. Shu'ba said:I bear witness to the fact that Allah's Messenger (ﷺ) gave judgment about it that a good quality of slave or female slave should be given for it. Thereupon 'Umar said: Bring one who may bear witness to you. Then Muhammad b. Maslama bore witness to him
Reference: Muslim 4397