Charles Ellicott Commentary Exodus 21:28-32

"And if an ox gore a man or a woman to death, the ox shall be surely stoned, and its flesh shall not be eaten; but the owner of the ox shall be quit. But if the ox was wont to gore in time past, and it hath been testified to its owner, and he hath not kept it in, but it hath killed a man or a woman, the ox shall be stoned, and its owner also shall be put to death. If there be laid on him a ransom, then he shall give for the redemption of his life whatsoever is laid upon him. Whether it have gored a son, or have gored a daughter, according to this judgment shall it be done unto him. 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 21:28-32 (ASV)

Injuries to the person might arise either from man or from animals. Protection from both was needed. The law given to Noah (Genesis 9:5) had already laid it down that whenever a beast killed a man, its life was to be forfeit. This law was now re-enacted, but with a further and very important proviso. If the animal had an owner, and the owner had reason to know that it was dangerous, then not only the beast, but the owner also was to be held guilty.

He was to be liable to a charge of murder (Exodus 21:29); but, with the consent of the aggrieved family, could pay a sum of money as compensation instead (Exodus 21:30). In the case of a slave, the sum was fixed at what was regarded as the standard price of a slave (Leviticus 25:44–46; Leviticus 27:3), namely, thirty silver shekels.