Numbers 35:21

Or in enmity smite him with his hand, that he die
Give him a blow with his fist, on some part of his body where life is most in danger, and which issues in death:

he that smote him shall surely be put to death, for he is a murderer;
and therefore, according to the original law, ought to die, without reprieve or pardon; and notwithstanding this law made for cities of refuge, which were to be denied him:

the revenger of blood shall slay the murderer when he meeteth him:
that is, when he is condemned, as both the Targums of Onkelos and Jonathan interpret it, after a hearing and trial of his case.