John Calvin on Exodus 21:32

32. 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. As regarded the crime of voluntary murder, there was no distinction between slaves and masters; but in a case of mischance (delicto) the severity might in some degree be mitigated; especially when the stoning of the ox sufficiently availed for bringing murder into detestation. God, therefore, showed admirable moderation in condemning the negligence of the master to be punished by the payment of thirty shekels; whilst He proposed the ox as an example, and reminded all by its death, how very precious in His sight is human blood.

Deuteronomy 17

Deuteronomy 17:6

6. At the mouth of two witnesses, or three witnesses, shall he that is worthy of death be put to death; but at the mouth of one witness he shall not be put to death.

6. In ore duorum vel trium testium interficietur qui moriturus est, non interficietur in ore unius testis.

Deuteronomy 19

Deuteronomy 19:15

15. One witness shall not rise up against a man for any iniquity, or for any sin, in any sin that he sinneth: at the mouth of two witnesses, or at the mouth of three witnesses, shall the matter be established.

15. Non stabit testis unus contra quenquam in quacunque iniquitate, et in quoeunque peccato quod peccaverit: in ore duorum testium vel in ore trium testium stabit verbum.