"Once you were not a people, but now you are the people of God; once you had not received mercy, but now you have received mercy." NIV translation
There is a very key truth in this verse but it is easily missed. The verse speaks of the fact that we were not always God's people because of sin and our will to do our own thing. But, we have received mercy through Jesus Christ and our relationship has been restored. We are now known as "the people of God" and a key word is "the". Today, there are many who are trying to make peace with different "religions" and are even going so far as to deny Jesus as the Son of God. This verse can remind us that there is only one way to be "the people of God" and that is through His Son. Anything other than that is quite simply a lie from the devil and his demons.
"Dear friends, I urge you, as aliens and strangers in the world, to abstain from sinful desires, which war against your soul." NIV translation
In this verse, Peter calls us to be holy and reminds us that this world is not our home. As aliens and strangers, we are called to be different and he reminds us that these sinful desires are battling against our soul. Each and every day, our flesh will try to get us to go one way but the Holy Spirit that is alive in us will try to get us to go God's way. As we grow in our Christian walk, we will be led more by the Spirit and be more conformed to the likeness of Christ.
"Live such good lives among the pagans that, though they accuse you of doing wrong, they may see your good deeds and glorify God on the day he visits us." NIV translation
Here, we see another reason for the call to holiness and that is to be a witness to those around us who do not know Jesus. We are called to "Live such good lives" (be holy) so that people around us cannot help but see God at work.
"Submit yourselves for the Lord's sake to every authority instituted among men: whether to the king, as the supreme authority, or to governors, who are sent by him to punish those who do wrong and to commend those who do right." NIV translation
As Christians, we are to be model citizens of our countries even though this is not our home. We are called to obey the laws of our land "for the Lord's sake". Jesus himself, when confronted by the authorities, submitted to them even to the point of death. Jesus even asked the Father to forgive them because they didn't know what they were doing. Just as Jesus prayed for the authorities, we should as well and we should pray that they would gain wisdom from God. Those who seek positions of authority should note that they will be held accountable for the manner in which they lead.