This is a huge question, and in a lot of ways it defies strict definition. What I mean is there is not some new list of rules and laws to keep, rather maturity in Christ is a process shaped by ongoing dialogue between you and God through His word, by His Spirit, and in community with other believers.
All three of these aspects (God's word, Spirit, and God's community) are all mentioned in the "going deeper" reading for this week.
(Read I Peter 2:4-12)
You see that right away in verse 4 Jesus is mentioned as "the living Stone", and believers are mentioned as "living stones" being built into a "spiritual house" to be "a holy priesthood, offering spiritual sacrifices acceptable to God through Jesus Christ."
So we see God's word coming alive in the person of Jesus, and we see the Holy Spirit building us up to be a "spiritual house" and "a holy priesthood". And this is where we see the community of believers. We are all together being built into "a spiritual house" and "a holy priesthood".
But what does "a holy priesthood" and "a spiritual house" look like today?
If we go to verses 9-10 we see the "holy (royal) priesthood" restated along with other descriptions of the community of believers: "a chosen people", "a holy nation", "a people belonging to God". We also see the reason we have been called by God to these roles "... that you may declare the praises of Him who called you out of darkness into His wonderful light."
But again how do we do that?
In verses 11-12, Peter offers sound instruction on what it means for us to live "in Christ".
He begins with what we should avoid, and goes onto what we should do.
So we should "abstain from sinful desires which war against our soul". Notice that Peter is not saying merely abstain from sinful actions, but even abstain from sinful desires. Recall that in James 1:14-15 the process leading to death is described. It begins with temptation combined with evil desire. It continues with desire giving birth to sin (action), and sin when it is full grown giving birth to death. So we can see in light of James, why Peter tells us to abstain from sinful desires because they truly do "war against our souls".
Now that Peter instructs us what to avoid, he leads us to see what we should do instead. "Live such good lives among the pagans that, ... they may see your good deeds and glorify God ..." So not only should we abstain from sinful desires, but we must also live good lives, which produce good, God-honoring deeds.
But again how do we do this?
Our ability to do what Peter instructs does not come from ourselves, it comes from God. The Holy Spirit works in us what is pleasing to Him. The Holy Spirit conforms us to the image of Jesus; God's Son. The Holy Spirit enables us to resist sin (even sinful desires) and empowers us to live good lives that honor God.
So now I am curious. What do you think this means for you today? What desires is God asking you to avoid, and what good, God-honoring deeds is He asking you to do instead? Let's be courageous and discuss this so we can help one another live according to all of God's truth.