Holiness, in its fullest sense, is not merely a static position but a process that must be perfected over time. While God can immediately sanctify something or someone—setting them apart for His use, as seen when holy brethren are described in Hebrews as those separated by God's calling rather than by their present character—this initial sanctification is only the beginning. Being called "holy brethren" refers to a state or position granted by God, not yet a reflection of what is truly in the heart or conduct of the individual. Just as inanimate things like the burning bush or the Ark could be declared holy solely by God's presence and decree, believers are first made holy by divine action rather than by their own merit. However, unlike inanimate objects, believers possess mind, will, and the capacity for choice, and therefore holiness must become an active, ongoing pursuit rather than a fixed status. Peter's instruction to "gird up the loins of your mind" signals that holiness demands preparation for action; it requires attitudes and choices leading to righteous conduct, not passive reliance on an initial calling. Before conversion, ignorance and self-satisfaction dominate, but God calls believers out of what is "profane"—a term meaning far from the Temple, the dwelling place of God. To be holy, then, is to separate from all that is profane and to pursue the divine likeness in every aspect of behavior. Central to this perfecting process is the Holy Spirit, since all holiness ultimately originates from God. Without the Spirit, the natural man cannot perceive or appreciate the beauty of holiness and is instead repelled by it, as seen in Isaiah's and Peter's reactions to divine holiness. Sanctification unto holiness begins only when one is confronted with truth, for Jesus prayed, "Sanctify them by Your truth. Your word is truth." God's Word functions as a living, penetrating force that exposes deception and cleanses the mind, and believers must digest and internalize this truth so that cleansing occurs from the inside out. As obedience to that word increases, genuine holiness—holiness "as God is holy"—begins to develop. Paul's exhortation in 2 Corinthians 7:1 makes the perfecting nature of holiness explicit: believers are called to "cleanse ourselves from all filthiness of the flesh and spirit, perfecting holiness in the fear of God." This perfecting is hindered when believers restrict themselves through wrong affections or unequal associations, as warned in 2 Corinthians 6:14-18, where believers are urged to be separate, to touch nothing unclean, and thereby to be received as God's sons and daughters. The transformative dimension of this process is described in 2 Corinthians 3:15-18: through the Spirit of the Lord, believers behold God's glory with unveiled faces and are "being transformed into the same image from glory to glory." Holiness, then, is perfected through the Spirit, through fellowship with God, and through faith and humility that produce obedience—ultimately transforming believers from the glory of man into the glory of God, a process without which, according to Hebrews 12:14, no one will see the Lord.

Holiness stands as the central quality required of anyone serving in a priesthood, and since God's purpose for His called-out people—under both covenants—is that they become a kingdom of priests, this quality takes on paramount importance for the church today. Scripture repeatedly commands "You shall be holy, for I am holy," from Leviticus through Numbers into Peter's epistle, showing that likeness to God in character is essential regardless of one's status, and that this standard remains unchanged in the New Covenant. Holiness identifies God's absolute uniqueness—He cannot be compared to any deity devised by men—and this uniqueness demands exclusive worship, reflected even in the first two commandments. Holiness is far more than morality; it encompasses infinite majesty, immeasurable power, and perfect righteousness, producing an awe that repeatedly drives people—Moses, Joshua, Isaiah, the disciples, Peter—to fall on their faces in humility and a sense of filthiness before God's overwhelming purity. Though believers are designated "holy" simply by virtue of their calling, this positional holiness must not be confused with the deeper quality of actually being made God-like, which can only occur through possession of God's spirit. The account of Moses' shining face after time in God's presence demonstrates that some measure of divine holiness can genuinely be imparted to those in intimate relationship with Him, teaching that holiness is attainable and not merely declared. This attainment comes through actual life experience within relationship with God—striving to live as Christ lived. Paul's exhortation to the Corinthians makes clear that believers, as the temple of God, must separate from uncleanness and go on "perfecting holiness in the fear of God," a process requiring self-control, self-denial, and cleansing from all filthiness of flesh and spirit. This perfecting is necessary because a temple must be kept clean for the sake of the One who dwells in it. Hebrews adds that believers must "pursue... holiness, without which no one will see the Lord," indicating that mere calling is insufficient—growth in holiness is required. Paul's prayer for the Thessalonians ties holiness directly to love, asking that God establish hearts "blameless in holiness" through love, and this appears immediately before a discussion of the resurrection, suggesting that growth in holiness bears directly on one's inclusion in that resurrection. The "beauty of holiness" imagery from the Psalms and Revelation, associated with priestly white robes and the righteous acts of the saints, illustrates worshiping God clothed in obedience. This attainment of holiness rests entirely on God's grace—His calling, granting of repentance, faith, and spirit—which should produce overflowing thanksgiving, itself a mark of humility and dependence that guards against falling for false doctrines. Ultimately, holiness is emphasized especially toward the priesthood because priests and Levites served as constant reminders that the whole nation, and now the whole church, is called to something far greater than merely avoiding sin: complete conformity to the holy nature of God, in preparation for the priestly role every believer is destined to fulfill in His Kingdom.