Question: "What does the Bible mean by 'an eye for an eye'?"
Answer: “Eye for eye, tooth for tooth” was spoken by God as a figurative command in the Old Testament (Exodus 21:24; Leviticus 24:20; Deuteronomy 19:21) and was never intended to be taken literally. Instead, it means is that secular justice is to be equitable, neither excessively harsh nor excessively lenient. In this connection there is no reference in Scripture to the maiming of a Hebrew in conformance with “eye for eye, tooth for tooth.” Also, before God first spoke this, He established a judicial system to hear claims and determine penalties (Exodus 18:13–26), and that system would not have been necessary if simple “eye for eye” retribution were proper and adequate. Moreover, most actual claims and harms in the Old Testament, except those requiring capital punishment, were settled by payment in goods.
The three times in the Old Testament where the phrase “an eye for an eye, and a tooth for a tooth” is mentioned all relate to a civil situation, something being judged before a duly constituted authority: a judge, a magistrate, etc. “An eye for an eye, and a tooth for a tooth” is not a statement that is in any way related to personal relationships. However, that’s precisely what the Pharisees had done with it. They took a divine principle for the courts, and they made it a matter of daily vendettas.
Knowing the hearts of the Pharisees, Jesus turned this phrase completely around. “You have heard that it was said, ‘An eye for an eye, and a tooth for a tooth.’ But I say to you…” (Matthew 5:38–48). Here Jesus was giving a new command that made perfect the Old Testament law. We are not to seek retribution, not to demand recompense for wrongs done to us. Rather, Jesus taught that as His followers we are to ignore all personal insults, which is the meaning of turning the other cheek. Christians are to give more of material goods, time, or labor than demanded of us, even if the demands are wrongful; to loan to those who want to borrow; to love our enemies; and to pray for those who persecute us.
The basis for this radically different way of dealing with one another underscores the radically different lifestyle of the true follower of Christ. But this is in no way to be taken as prohibiting self-defense or protecting someone from being harmed by others. The rights of police officers and the military to protect the innocent and preserve the peace are not in question here. Turning the other cheek applies to personal relationships and involves primarily not seeking to defend ourselves against personal insults.