Persecution is therefore not a cause for fear, but rather an opportunity to honor Christ and revere him as Lord (as opposed to Caesar!) Peter is not commanding a completely passive acceptance of suffering. Rather, he tells the readers to be ready to give an answer when asked about their hope in Christ (v. 15b). Typically this verse is used to encourage people to know what they believe and why they believe it.
This is a good application (and it is true that you ought to know why you believe what you do), but Peter has in mind believers who are being unfairly harassed because of their faith in Jesus. Although it may not be the case than anyone has 
The command is to be prepared, meaning that the believer has already knows why they are willing to put up with harassment for their faith. To prepare something is to do the work ahead of time. The word “always” or “constantly” also implies that the reasons for one’s faith are prepared and always available. Peter does not envision a sudden rush of the Holy Spirit inspiring someone to give a good defense, rather the believer has ready an explanation for why they are humbly suffering for their faith.
By way of analogy, if someone is called into court on some charge, a lawyer “prepares a case.” this means there is some investigation of the evidence so that the lawyer can anticipate questions and give a good answer. A lawyer who comes into court without ever looking at the case ahead of time will fail and the person under arrest will be convicted.
This defense is to be “with gentleness and respect.” Since the Roman world was used to verbal abuse between philosophical schools, it would be very easy for the Christian to give his defense of his faith with the same sort of abuse the orator heaps on his opponents.
This is a very convicting verse since there are many Christians who have no idea what they believe, or if they do know what they believe, they are unable to give much of a reason for that belief. (The old hymn, I need no other argument, I need no other plea, it is enough that Jesus died, and that he died for me – that is a nice sentiment, but perhaps knowing a little bit of the “device or creed” will help confirm one’s faith when suffering does occur!)
The “hope we have” should be taken as eschatological. In the midst of suffering, the believer can know than Jesus is going to return at some point at render justice. For the believer, that means vindication (they were suffering unjustly) and reward, but for the persecutor, it means punishment.
The point of all of this is that the Christian ought to maintain a clear conscience so the outsider will be ashamed to slander the Christian faith (v. 16). This seems to me to be opposite of Christianity in recent years, or perhaps it only seems so because the media is able to broadcast a few particularly shameful examples of Christian hypocrisy. Think for a moment about presidential candidates claiming to be Christian yet giving hate-filled and vulgar speeches.
Rather than dwell on people who are shameful yet claim to be believers, what are some positive examples of Christians who are living out this “patient suffering” and have given outsiders no reason to slander them?
in Judea, Peter tells his readers to channel their zeal into a quiet life that is worthy of respect.
Unity of mind (ὁμόφρων). This word means something like “thinking the same things.” The Greco-Roman world appreciated traditions that held communities together, especially in families. It is shameful for families to disagree among themselves, or for brothers to fight among themselves. While the modern world commonly has families with several religions or political associations, that simply did not happen in the Roman world. Families were defined by their common beliefs that everyone held. For Peter, the Christian community has a set of beliefs and values that define it as a “family” so that outsiders can see that there is no discord within the family.
Unlike the slaves and the wives, the husband is told to live with their wives in an “understanding way.” The way this is stated makes is sound as though the husband is to have a kind and tender heart toward his wife, and that is certainly part of the point. But Peter is saying that the husband must live with his wife fully aware of who she is and with full awareness of his responsibility toward her.
Peter’s words cannot be taken as an endorsement of misogyny, however. In fact, Peter tells the husbands to honor (τιμή) their wives, the same word he used for “honor the emperor” (τιμάω) in 2:17. Imagine that a husband gave his wife the same honor demanded of the Roman emperors!