أَخْبَرَنَا مُحَمَّدُ بْنُ عُبَيْدِ اللَّهِ بْنِ يَزِيدَ، قَالَ حَدَّثَنَا عُثْمَانُ بْنُ عَبْدِ الرَّحْمَنِ الطَّرَائِفِيُّ، قَالَ حَدَّثَنَا مُعَاوِيَةُ، عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ نَبِيَّ اللَّهِ صلى الله عليه وسلم قَضَى فِي الْمُكَاتَبِ أَنْ يُودَى بِقَدْرِ مَا عَتَقَ مِنْهُ دِيَةَ الْحُرِّ ‏.‏

It was narrated from Ibn 'Abbas that: the Prophet of Allah ruled that the Diyah for a Mukatab should be (equivalent) to the Diyah for a free man, proportionate to the amount he had paid off (toward buying his freedom). Translation Not Available

Book Ref: Sunan An Nisai Book 45 Hadith 4809
Web Ref:  Sunan An Nisai Vol 5 Book 45 Hadith 4813