When Peter says “Be holy for the Lord is holy” he’s obviously encouraging us to pursue likeness to God. But precisely where do we look to find this?
I think holiness needs to be seen in a Trinitarian framework where we think of imitating the Father, Son and Holy Spirit.
When God says “be holy for I am holy” I think He wants us to imitate Him as Father – as one who is separated and consecrated. We are meant to be like our heavenly Father in righteousness, holiness and in integrity. That means we are to strive to be of the same character as God.
Second, holiness is a call to be conformed to the image of Christ. This is a favourite Pauline theme, “let this mind be in you which was also in Christ Jesus” (Phil. 2:5). Christ was humbled; Christ was willing to give up His rights to obey God and serve sinners. So Paul is saying, if you’re going to be holy, you have to be like-minded with the Lord Jesus. And that, of course, is the lifelong challenge of a Christian. We’re always looking to Christ for holiness – He’s the fountain of holiness and the path to it. We don’t need another path; we just have to strive to walk along that path. Augustine put it well when he said, “It’s better to limp on the path of holiness in Christ than it is to run outside of that path.” Calvin said something similar: “Set Christ before you as the mirror of sanctification and then seek grace to mirror Him in His image.” And so the Christian is involved in an unending pursuit to be more like Christ. Paul sums it up well when he says that we have been “predestined to be conformed to the image of the Son” (Rom. 8:29).
Finally, holiness also involves submission to the mind of the Holy Spirit. Paul makes that clear in Rom 8:6 where he actually divides everyone into two categories – those who are controlled by their sinful natures and those who follow after the Spirit. The Spirit shows us our need for holiness, implanting desires in us for it, making us more Christ-like and then providing strength for us to live a holy life by His own indwelling influences. He does this through our use of the means of grace.
– Dr Joel Beeke