Numbers 35:22-24

Brenton(i) 22 But if he should thrust him suddenly, not through enmity, or cast any thing upon him, not from an ambuscade, 23 or smite him with any stone, whereby a man may die, unawares, and it should fall upon him, and he should die, but he was not his enemy, nor sought to hurt him; 24 then the assembly shall judge between the smiter and the avenger of blood, according to these judgments.