God is Holy. The Psalmist proclaimed, Exalt the Lord our God, And worship at His holy hill; for the Lord our God is holy (Psalm 99:9).
Because God is holy, supplicants who approach Him must be holy as well. Nadab and Abihu, the sons of Aaron, profaned themselves before God when they offered up strange fire by way of sacrifice. In punishment, God took their lives. And Moses said to Aaron, This is what the Lord spoke, saying: By those who come near me I must be regarded as holy; and before all people I must be glorified. So Aaron held his peace (Leviticus 10:3).
This call to holiness is fully realized in the term sanctification. The term sanctification is used, as pointed out by Vine, of (a) separation to God; (b) the course of life befitting those so separated. (pg. 317).
The first point, that we have been separated to God, is indicated clearly in 2 Thessalonians 2:13-14, But we are bound to give thanks to God always for you, brethren beloved by the Lord, because God from the beginning chose you for salvation through sanctification by the Spirit and belief in the truth, to which He called you by our gospel, for the obtaining of the glory of our Lord Jesus Christ. God chose us to be separate from the world, and called us by his gospel. Paul stated this clearly in Ephesians 1 as he indicated that God chose us in Christ before the foundation of the world, that we should be holy and without blame before Him in love (vs. 4). Those who respond to the gospel of Christ, through baptism, die to sin and are reconciled to God. They are sanctified.
The second point, that our lives should befit those who are separated to God, indicates a need for holiness, which is intrinsic in the term. As the apostle Paul pointed out in calling the Thessalonians to moral purity, possess [-ing] his own vessel in sanctification and honor, not in passion of lust, like the Gentiles who do not know God, when he wrote, For God did not call us to uncleanness, but in holiness (1 Thessalonians 4:4-5, 7). Because we are called to God, we should live holy lives. As Paul wrote, For the grace of God that brings salvation has appeared to all men, teaching us that, denying ungodliness and worldly lusts, we should live soberly, righteously, and godly in the present age (Titus 2:11-12).
Such a call to live holy lives is not arbitrary, it is founded in Gods character. But as He who called you is holy, you also be holy in all your conduct, because it is written, Be holy, for I am holy (1 Peter 1:15-16). Too often in our time the concept of morality is considered arbitrary and antiquated. Some reason that it may have served man in times past, but in our enlightened time, we have no need of unchanging standards based upon religious faith. To these foolish people, morality is situational, and virtues such as honesty, modesty, humility, and temperance are to be utilized only as they serve the whim of the individual. In response to such thinking the prophet Jeremiah wrote, O Lord, I know the way of man is not in himself; it is not in man who walks to direct his own steps (Jeremiah 10:23).
Because God is holy, his call for man to be holy is proper. I beseech you therefore, brethren, by the mercies of God, that you present your bodies a living sacrifice, holy, acceptable to God, which is your reasonable service. And do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what is that good and acceptable and perfect will of God (Romans 12:1-2).
We are to live moral lives because God is holy. We are to conform our teaching to Gods will because God is holy. We are to dress with propriety and modesty because God is holy. We are to be reverent before God in worship and demeanor because God is holy.
Every aspect of our lives is impacted by Gods holiness. The perfect sinlessness of the Son of God should ever be fefore us. For to this you were called, because Christ also suffered for us, leaving us an example, that you should follow His steps: Who committed no sin, Nor was deceit found in His mouth (1 Peter 2:21-22). The holiness of God is awesome, and should inspire in us a quiet reverence, and a holy life.
But the Lord is in His holy temple. Let all the earth keep silence before Him (Habakkuk 2:20).