Jamieson, Fausset and Brown on Exodus 21:28-36

28-36. If an ox gore a man or a woman, that they die--For the purpose of sanctifying human blood, and representing all injuries affecting life in a serious light, an animal that occasioned death was to be killed or suffer punishment proportioned to the degree of damage it had caused. Punishments are still inflicted on this principle in Persia and other countries of the East; and among a rude people greater effect is thus produced in inspiring caution, and making them keep noxious animals under restraint, than a penalty imposed on the owners.