Sunnah.com reference : Book 15, Hadith 16English translation : Book 15, Hadith 1477Arabic reference : Book 15, Hadith 1433
Ibn ’Abbas (RAA) narrated that The Messenger of Allah (ﷺ) said:
“The Diyah (Blood money) of a slave who had made an agreement to buy his freedom (Mukatib) and had been killed, is paid at the rate paid for a free man (as a Diyah) as much as he has paid of the amount agreed upon, and at the rate paid for a slave as the remainder is concerned.” Related by Ahmad, Abu Dawud and Au-Nasa’i.
وَعَنْ اِبْنِ عَبَّاسٍ ‏-رَضِيَ اَللَّهُ عَنْهُمَا‏- أَنَّ اَلنَّبِيَّ ‏- صلى الله عليه وسلم ‏-قَالَ: { يُودَى اَلْمُكَاتَبُ بِقَدْرِ مَا عَتَقَ مِنْهُ دِيَةَ اَلْحُرِّ, وَبِقَدْرِ مَا رَقَّ مِنْهُ دِيَةَ اَلْعَبْدِ }  رَوَاهُ أَحْمَدُ, وَأَبُو دَاوُدَ, وَالنَّسَائِيّ ُ  1‏ .‏‏1 ‏- صحيح.‏ رواه أحمد (1 / 222‏- 223 و 226 و 260)‏، وأبو داود (4581)‏، والنسائي (8 / 46)‏ واللفظ لأحمد.‏