In II Corinthians, Paul stresses the need for believers to separate themselves from what defiles—evil. His concluding instruction is that the fear of God is the means by which we accomplish this perfecting of holiness:
Do not be unequally yoked together with unbelievers. For what fellowship has righteousness with lawlessness? And what communion has light with darkness? And what accord has Christ with Belial? Or what part has a believer with an unbeliever? And what agreement has the temple of God with idols? For you are the temple of the living God. As God has said: "I will dwell in them and walk among them. I will be their God, and they shall be My people." Therefore "Come out from among them and be separate, says the Lord. Do not touch what is unclean, and I will receive you." 'I will be a Father to you, and you shall be My sons and daughters,' says the LORD Almighty." Therefore, having these promises, beloved, let us cleanse ourselves from all filthiness of the flesh and spirit, perfecting holiness in the fear of God. (II Corinthians 6:14-18; 7:1)
We who believe in Christ's name, who have received Him, have been given the right—the authority—to become children of God (John 1:12). If we, as Paul instructs, separate ourselves from what is unclean, we will be His sons and daughters. Children resemble their parents, and one way that we learn to resemble God is by loving the things that He loves and hating the things that He hates. God hates those things that harm the life and liveliness of His current and future children. As we grow in His image, we should also hate what is evil. That is one way that we fear and respect Him.
The more we fear and reverence the holiness of God, the more we grasp our own flaws and defilement. This, in turn, causes us to hate the evil that we find within ourselves (Matthew 5:3-4, 6) and to despise the elements of our nature that would make us miserable or that would cause misery in others if they were allowed to continue forever.
Yet, identifying those things is impossible without allowing the light of truth to shine into our lives. That light comes through knowing God and Jesus Christ. Knowing Them helps us to develop the proper fear of God, and at the same time it helps us to begin to see, by contrast, what things in us cause harm to life and liveliness.