Numbers 35:22-25

But if a man has given a wound to another suddenly and not in hate, or without design has sent something against him, Or has given him a blow with a stone, without seeing him, so causing his death, though he had nothing against him and no desire to do him evil: Then let the meeting of the people be judge between the man responsible for the death and him who has the right of punishment for blood, acting by these rules: And let the people keep the man responsible for the death safe from the hands of him who has the right of punishment for blood, and send him back to his safe town where he had gone in flight: there let him be till the death of the high priest who was marked with the holy oil.