1 Peter 1:14-16 (AMP) 14 [Live] as children of obedience [to God]; do not conform yourselves to the evil desires [that governed you] in your former ignorance [when you did not know the requirements of the Gospel]. 15 But as the One Who called you is holy, you yourselves also be holy in all your conduct and manner of living. 16 For it is written, You shall be holy, for I am holy.
There is a difference between believing in God and living your life because you believe in God. We need to be holy in the way we live, deal with people, talk, think, what we do for entertainment, etc. You shall be holy is a promise that God has made us holy because of His love for us. God will help us to live a holy life so we don’t have to be on our own trying to make right choices. God knows we are going to make mistakes that’s why he gives us His holiness as a free gift. He’s there for our successes and He is there for our failures. But God’s holiness is there for us just as we have never sinned.
God gives us the equipment we need to be in the world and be a great representative for Him.