11 Beloved, I urge you as aliens and exiles to abstain from the desires of the flesh that wage war against the soul. (NRSV)
I find this verse hard to move past. Mainly because it speaks to me quite deeply. We need to think carefully about what it does and doesn't mean, but the personal force of it is impossible to sidestep.
The warning is not to read this verse in a dualistic fashion. Here's how this might look
Beloved, I urge you as those in exile on earth, waiting to go to heaven, to abstain from the desires of the body that wage war against your eternal souls, bound for heaven.
The problem with flesh versus soul is that we immediately jump to physical versus spiritual. It doesn't help if you see exile in purely spiritual terms and not in social terms as Scott McKnight does - though there is no doubt we are exiles in a world where God's kingship is not clear to all. Here's another way of looking at it
Beloved, I urge you as outsiders in an ungodly world to abstain from the desires of the unregenerate part of your humanity that wage war against you.
So apart from the sociopolitical comments (see a couple of posts ago), it isn't about things of the body versus spiritual matters, but that part of us that isn't transformed versus who we are to be. To be sure, the word for flesh is used to describe our material bits at times, but the Greek word soma is used more for that than the word sarx (of form of which is used here). In other words, it isn't the body, the physical stuff which is somehow evil, but the desires unchecked, passions at war with our true identities. Soul is most often used in the Old Testament to mean the whole person. Sometimes in the New Testament, Paul will use soulish as opposite to spiritual, but we can't always use Paul to interpret Peter.
So given that is cleared up, it is clear that our desires can war against us. There is real struggle, real angst, real frustration and often a real sense of defeat. But of course we know in Christ that while the battle rages, the war has been won.
We are called to abstain. Now abstinence is not a popular idea in today's world - probably a topic for another time. Think about voting. If you abstain, you refuse to vote. You refuse to countenance what is being raised. In abstaining, we refuse to give credence to fleshly desires, refuse to acknowledge their validity. We step outside of that world and not take part.
This is easier said than done when so much of this is internal, within us and not merely without. This is why it is a spiritual thing - why we need the Holy Spirit to help us discipline ourselves, hence prayer, fasting(?), bible reading, etc. Once that battle has started, we are equipped for the external factors - changing friendships, web filters, whatever can act as an external aid to avoid temptations. I feel some reflections on the full armour of God coming on, but another time.