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. (JA)
English reference (JA): Book 9, Hadith 1216 (JA)
Arabic reference (JA): Book 9, Hadith 1186 (JA)