Definition and Nature:
God's absolute holiness is a fundamental attribute of His divine nature, signifying His complete separation from sin and moral imperfection. Holiness, in the biblical context, refers to God's purity, righteousness, and the transcendence of His character. It is not merely an aspect of God but the very essence of His being, permeating all His attributes and actions.

Biblical Foundation:
The concept of God's holiness is deeply rooted in Scripture, where He is often described as "holy, holy, holy" (Isaiah 6:3; Revelation 4:8), emphasizing the superlative degree of His holiness. This thrice-repeated declaration underscores the perfection and completeness of His holy nature.

Old Testament Revelation:
In the Old Testament, God's holiness is revealed through His interactions with His people and His commandments. The book of Leviticus, for instance, is replete with references to God's holiness, as He commands His people to be holy because He is holy (Leviticus 11:44-45). The holiness of God is also demonstrated in His separation from sin and His intolerance of impurity, as seen in His dealings with Israel and the sacrificial system designed to atone for sin and maintain the sanctity of His people.

The prophet Isaiah's vision of the Lord in the temple (Isaiah 6:1-5) provides a profound depiction of God's holiness. Isaiah's immediate recognition of his own sinfulness in the presence of the Holy One highlights the stark contrast between God's purity and human imperfection.

New Testament Revelation:
In the New Testament, God's holiness is manifested in the person and work of Jesus Christ. Jesus, as the incarnate Son of God, embodies divine holiness, living a sinless life and fulfilling the righteous requirements of the law. The holiness of God is further revealed through the Holy Spirit, who sanctifies believers and empowers them to live holy lives (1 Peter 1:15-16).

The apostle John, in his first epistle, affirms the holiness of God by declaring, "God is light, and in Him there is no darkness at all" (1 John 1:5). This metaphor of light underscores the purity and moral perfection inherent in God's nature.

Implications for Believers:
God's absolute holiness has profound implications for believers. It calls for a response of reverence, worship, and a commitment to personal holiness. The call to holiness is a recurring theme in the New Testament, where believers are exhorted to "be holy in all your conduct" (1 Peter 1:15) and to "present your bodies as a living sacrifice, holy and pleasing to God" (Romans 12:1).

The holiness of God also assures believers of His faithfulness and justice. Because God is holy, He is trustworthy and unchanging, and His promises are sure. His holiness guarantees that He will ultimately judge sin and establish righteousness.

Conclusion:
While God's absolute holiness is beyond full human comprehension, it is a central tenet of the Christian faith, shaping the believer's understanding of God's character and their relationship with Him. The call to holiness is both a privilege and a responsibility, reflecting the transformative power of God's holy presence in the life of the believer.