It was narrated that Ibn '‘Abbas (رضي الله عنه) said:

The Messenger of Allah (ﷺ) ruled concerning a mukatab (a slave who has a contract of manumission), if he is killed, the diyah of a free man should be paid, commensurate with how much of his contract of manumission he had paid off, and the rest should be paid as the diyah of a slave.