Translation
(41) Types of Blood-Wit (Kitab Al-Diyat)
كتاب الديات
(1650) Chapter: If A Man Kills His Slave Or Mutilates Him, Should Retaliation Be Imposed On Him ?
(7) باب مَنْ قَتَلَ عَبْدَهُ أَوْ مَثَّلَ بِهِ أَيُقَادُ مِنْهُ
Sunan Abi Dawud 4518 
It was narrated from Hisham, from Qatadah, from Al-Hasan, who said:
"A free man should not be subjected to retaliation in return for a slave."
حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا هِشَامٌ، عَنْ قَتَادَةَ، عَنِ الْحَسَنِ، قَالَ لاَ يُقَادُ الْحُرُّ بِالْعَبْدِ ‏.‏
Grade :  Sahih Maqtu' (Al-Albani) صحيح مقطوع  (الألباني)حكم :
Reference : Sunan Abi Dawud 4518
In-book reference : Book 41, Hadith 25
English translation : Book 40, Hadith 4503