Lev. 27:1-7 shows that persons were valued, depending on strength (sex and age) at between three and fifty shekels of silver. Thirty, then, is a good average; and in the case of the slave killed by the ox, thirty shekels of silver was mandatory (Exo. 21:32). This puts the slave in the same category as the animal in Exo. 21:36. If a notorious ox kills another ox, the owner simply has to make it good. But, that is part of the risk of slavery; you might be gored by an ox. It is best to avoid slavery if you can. The Bible wants the slave to save his money and buy his freedom, or become adopted into the master's household as a son-servant.
- James Jordan, The Law of the Covenant 127 (1984), at http://www.garynorth.com/freebooks/: HTML, DjVu.