Peter's words are intended, not merely to instruct, but also to encourage. We listen to God's Word because God Almighty Himself personally chose us to do so. That needs to sink into our brains and become part of how we operate our lives. We are the chosen of God, elect according to His foreknowledge. That is, before we ever knew of the true God, He was watching us. He was monitoring us and waiting for the opportunity that, at just the right time, He would reveal Himself to us in just the right circumstance, just the right environment to give us the best opportunity to respond to the truth.
We can expand this process out to include the whole church. The church exists because God willed it so. The church does not exist because of human goodness, hopes, aspirations, vision, or dreams. It exists because of the eternal purpose of God, which is both a tremendous honor and responsibility.
God, working through His Spirit (notice, "in sanctification of the Spirit"), sets us apart, consecrates us, or makes us fit for His calling. God is a creator. That fact is what Peter explains here. His calling is the first step to prepare us to inherit His Kingdom. We should not limit the calling just to the initial time that He entered our lives, and we began to understand. His calling ultimately includes the whole process.
Peter states the goal He has in mind as "obedience and sprinkling of the blood of Jesus Christ." It is the Spirit of God that makes the calling of God effective. It is a singular act, but at some time in our lives, He "messed with" our brain—He turned the light on—and we began to respond. He did this as a singular act at a specific time, but His calling is also a process that begins with that initial act and ends with resurrection into His Family. The sanctification of the Spirit of God ties all of it together.
The initial act by God opens our mind, which is the beginning of sanctification. It is like being given a second start, which Paul calls "regeneration" (Titus 3:5). Then comes the sanctification that arises with growth, overcoming, and becoming more like God. Finally, there is glorification, which is the ultimate in sanctification. The whole process is encompassed by the calling of God, and the Spirit of God ties all of these steps together.