The short answer: Holiness. God’s and our own.
1 Peter 1:13-16 – “Therefore, get your minds ready for action, being self-disciplined, and set your hope completely on the grace to be brought to you at the revelation of Jesus Christ. As obedient children, do not be conformed to the desires of your former ignorance but, as the One who called you is holy, you also are to be holy in all your conduct; for it is written, Be holy, because I am holy.” (Holman Christian Standard Bible)
I am a novice at this topic but I am learning. Jerry Bridges wrote a book called The Pursuit of Holiness and his teachings so far have been very insightful. Here are some excerpts to hopefully motivate any of my readers who desire this for their own life:
“The concept of holiness may seem a bit archaic to our current generation. To some minds the very word holiness brings images of bunned hair, long skirts, and black stockings. To others the idea is associated with a repugnant “holier than thou” attitude. Yet holiness is very much a scriptural idea. The word holy in various forms occurs more than 600 times in the Bible…More important, God specifically commands us to be holy…”
(cont.) “…The idea of exactly how to be holy has suffered from many false concepts. In some circles, holiness is equated with a series of specific prohibitions – usually in such areas as smoking, drinking, and dancing. The list of prohibitions varies depending on the group. When we follow this approach to holiness, we are in danger of becoming like the Pharisees with their endless lists of trivial do’s and don’ts, and their self-righteous attitude. For others, holiness means a particular style of dress and mannerisms. And for still others, it means unattainable perfection, an idea that fosters either delusion or discouragement about one’s sin.”
“All of these ideas, while accurate to some degree, miss the true concept. To be holy is to be morally blameless. It is to be separated from sin and, therefore, consecrated to God. The word signifies “separation to God, and the conduct befitting those so separated.”” (pp. 16-17)
He goes on to list three reasons why Christians struggle with the idea and aspect of living in holiness:
1. our attitude toward sin is more self-centered than God-centered
2. we have misunderstood “living by faith” (Gal. 2:20) to mean that no effort at holiness is required on our part
3. we do not take some sin seriously
There is so much in the book that I cannot unpack here. Let me encourage you with Paul’s exhortation to the church at Philippi: “So then, my dear friends, just as you have always obeyed (and if not, then start obeying now), not only in my presence, but now even more in my absence, work out your own salvation with fear and trembling. For it is God who is working in you, enabling you both to will and to act for His good purpose. Do everything without grumbling and arguing, so that you may be blameless and pure, children of God who are faultless in a crooked and perverted generation, among whom you shine like stars in the world. Hold firmly the message of life.” (2:12-16a; italics added).
Be holy, because our God is holy. His commands are not grievous, and if we love God we will obey what He commands, for God is love.