It is narrated from Sa'id bin al-Musayyib, may Allah have mercy on him, that he said: "The blood money (diyah) of a slave is in his value, just as the wound of a free man is in his blood money (diyah)."
Hadith Referenceمسند الإمام الشافعي / كتاب القتل والقصاص والديات والقسامة / 1654
Hadith Takhrijاسناده صحيح اخرجه البيهقي: 104/8 - وفي المعرفة السنن والآثار له (4940) - وعبدالرزاق (18142)۔ و ابن ابى شيبة (27219)۔