Joshua 20:3

That the slayer that killeth [any] person unawares, [and]
unwittingly, may flee thither
Who through mere accident, and without design, killed a person, friend or foe, one of his own kindred, or a stranger, without any malice against him, or intention to take away his life:

and they shall be your refuge from the avenger of blood;
from any of the relations of the deceased, who might be stirred up to avenge the blood of his kinsman on the slayer; see ( Numbers 35:12 ) .