What is holiness according to the Bible? How can I be holy?

from the old testament

• God repeatedly identifies Himself as holy, completely set apart, morally pure, and distinct from sin (Leviticus 11:44–45; Isaiah 6:3). Holiness is intrinsic to God, and He expects His people to reflect His character.
• Leviticus 19:2 commands, “You shall be holy, for I the Lord your God am holy.” Holiness is not optional; it is a divine calling for all who belong to God.
• The Israelites were instructed to avoid defilement, idolatry, and immoral practices (Leviticus 20; Deuteronomy 7:1–6). Being holy means living differently from the surrounding culture.
• Following God’s laws and commandments was a tangible way to live out holiness (Exodus 19:5–6; Deuteronomy 6:4–5).
• The prophets emphasized that ritual observance without a righteous heart was meaningless (Hosea 6:6; Isaiah 29:13). True holiness comes from a heart surrendered to God.

from the new testament

• In 1 Peter 1:16 we read, “You shall be holy, for I am holy.” The word translated “holiness” in the New Testament means to be “set apart.”
• All people have sinned (Romans 3:23) and are imperfect. Our only option to be set apart is through the salvation offered through Jesus Christ (John 3:16; Romans 10:9; Ephesians 2:8-9). When we believe in Jesus as Lord, He cleanses us from sin and makes us holy (1 John 1:7). Theologians often refer to this concept as positional sanctification.
• First Peter 2:9 speaks of this new status as well: “But you are a chosen race, a royal priesthood, a holy nation, a people for his own possession, that you may proclaim the excellencies of him who called you out of darkness into his marvelous light.” God calls us holy even though we still commit sins during this life.
• In addition to being made holy, we are called to live holy lives. “As obedient children, do not be conformed to the passions of your former ignorance, but as he who called you is holy, you also be holy in all your conduct” (1 Peter 1:14-15). We are commanded to avoid the ways we practiced before becoming a Christian and live according to God’s ways. We can only do this by living by the power of God's Spirit, following the principles found in God's Word.

implications for today

When we are saved, we are made positionally holy, set apart to live for God. In addition, we are called to obey God and grow in holy living each day. Theologians refer to this daily practice of living for God to become more holy as progressive sanctification. As we seek to follow God’s will each day, we can increasingly become holy as we become more like Christ. Our goal should be to say like Paul, “Be imitators of me, as I am of Christ” (1 Corinthians 11:1).

Regardless of the progress we make to become more holy in this life, we will never be perfect. We will still sin at times, as Paul wrote in Romans 7:18b-19, “For I have the desire to do what is right, but not the ability to carry it out. For I do not do the good I want, but the evil I do not want is what I keep on doing.” It will only be in heaven that all sin will be removed from our lives and we are made perfect. Theologians refer to this as glorification.

Still, God can and will work in our lives to help us better live for Him. We may not be sinless, we can sin less as we seek to be holy as He is holy. After this life, we can anticipate a perfect, eternal existence with God in which we no longer sin and are made perfectly holy, living in the presence of God forever.