Abil Shuraih Al-Khaza'i (RAA) narrated that The Messenger of Allah (ﷺ) said:
"If the relative of one of you is killed after my speech, his family has one of two choices: 'Either they take his Diyah or kill the killer." Related by Abu Dawud and An-Nasa'i. (ID)
English reference (ID): Book 9, Hadith 1216 (ID)
Arabic reference (ID): Book 9, Hadith 1186 (ID)