John Calvin Commentary Exodus 21:32

"If the ox gore a man-servant or a maid-servant, there shall be given unto their master thirty shekels of silver, and the ox shall be stoned." — Exodus 21:32 (ASV)

If the ox shall push a man-servant. It is not unreasonable that the punishment for the death of a slave should now be set at less than for that of a free-man. Regarding the crime of voluntary murder, there was no distinction between slaves and masters; but in a case of mischance (delicto), the severity might be somewhat mitigated, especially when the stoning of the ox sufficiently served to bring murder into detestation. God, therefore, showed admirable moderation in condemning the negligence of the master to be punished by the payment of thirty shekels, while He presented the ox as an example and reminded all by its death, how very precious in His sight is human blood.