Or HaChaim on Exodus 21:30/אור החיים על שמות כ״א:ל׳

1 פדיון נפשו. His soul's ransom. There is a dispute in Baba Kama 40 as to what determines the amount of compensation. Some hold that we evaluate the worth of the victim that has died, others that the basis of the compensation is the value of the offending animal. According to the opinion that we determine the amount of compensation based on the value of the ox which gored, it would appear that where the ox in question was owned by more than one individual each one has to pay the full amount of compensation seeing there is no death sentence by a human tribunal which would override the laws of financial compensation. According to the opinion that the basis of the compensation is the value of the victim, the offenders would only have to share the monetary value of the victim between them. In view of this, the question Rabbi Nachman asked Rabbi Acha bar Yaakov whether both owners have to pay compensation seems out of place, seeing this is a much older Tannaitic argument. Clearly, we cannot assume that the question mentioned in the Talmud is based on the assumption that the value of the offending ox is the basis of the compensation [which everyone agrees serves as atonement not as restitution, Ed.]. In the following scenario an ox worth 200 shekel has gored a human being whose market value as a slave would have been 50 shekel. If the ox was owned by more than one party, and the basis of compensation is the value (maximum) of the offending ox, each owner pays 50 shekels. No allowance is made for the fact that there are two owners who could have shared the damage of 50 shekels that had been inflicted. The problem Rabbi Nachman submitted to Rabbi Acha bar Yaakov was based on the assumption of the Chachamim that the value of the victim serves as the basis of the compensation. It appears that Maimonides also understood the problem in this way for he ruled in chapter 11 of his Hilchot Nizkey Mamon that monetary compensation is based on estimating the value of the slain person (or animal); if two people owned the offending animal, each partner has to pay compensation equivalent to the total value of the victim. The reason Maimonides takes the stricter view is because we have a doubt as to whose opinion is correct, and when matters of compensation for a life taken is involved we always accept the stricter view when in doubt.

2Should the avenger of the victim have succeeded in killing the owner of the offending animal before the latter had a chance to make the compensatory payment, I believe the avenger is guilty of murder. The Torah law covering the avenger is applicable only if the killer had killed by his own hand, not when his property was the instrument causing the death.