Definition and Nature:
God's unchanging holiness is a fundamental attribute of His divine nature, signifying His absolute moral purity, separateness from sin, and perfect righteousness. Holiness is intrinsic to God's being, and it is immutable, meaning it does not change over time or under any circumstances. This attribute sets God apart from all creation and establishes the standard for moral and ethical conduct.

Biblical Foundation:
The Bible consistently affirms God's holiness. In Isaiah 6:3, the seraphim proclaim, "Holy, holy, holy is the LORD of Hosts; His glory fills the whole earth." This thrice-repeated declaration emphasizes the supreme and unparalleled holiness of God. Similarly, in Revelation 4:8, the four living creatures continually say, "Holy, holy, holy is the Lord God Almighty, who was, and is, and is to come!" These passages underscore the eternal and unchanging nature of God's holiness.

God's Holiness in the Old Testament:
The Old Testament frequently highlights God's holiness as a defining characteristic. In Leviticus 11:44, God commands His people, "For I am the LORD your God. Consecrate yourselves therefore, and be holy, because I am holy." This call to holiness reflects God's desire for His people to mirror His moral purity and separateness from sin. The holiness of God is also evident in His interactions with humanity, as seen in the encounter between Moses and God at the burning bush, where God instructs Moses to remove his sandals because the ground is holy (Exodus 3:5).

God's Holiness in the New Testament:
The New Testament continues to affirm God's unchanging holiness. In 1 Peter 1:15-16, believers are exhorted, "But just as He who called you is holy, so be holy in all you do, for it is written: 'Be holy, because I am holy.'" This reiteration of the call to holiness demonstrates the continuity of God's moral standard from the Old Testament to the New Testament. Furthermore, the holiness of God is manifested in the person of Jesus Christ, who lived a sinless life and perfectly embodied God's holy nature.

Implications for Believers:
God's unchanging holiness has profound implications for believers. It serves as the foundation for the moral and ethical standards to which Christians are called. Believers are urged to pursue holiness in their own lives, striving to reflect God's character in their thoughts, words, and actions. Hebrews 12:14 admonishes, "Pursue peace with everyone, as well as holiness, without which no one will see the Lord." This pursuit of holiness is not merely an external adherence to rules but a transformation of the heart and mind, enabled by the Holy Spirit.

God's Holiness and Justice:
God's holiness is inseparably linked to His justice. Because God is holy, He cannot tolerate sin and must judge it righteously. Habakkuk 1:13 declares, "Your eyes are too pure to look upon evil, and You cannot tolerate wrongdoing." This aspect of God's holiness underscores the necessity of atonement and the redemptive work of Christ, who bore the penalty for sin, satisfying the demands of God's justice while upholding His holiness.

God's Holiness and Worship:
The recognition of God's unchanging holiness is central to worship. Believers are called to approach God with reverence and awe, acknowledging His majesty and purity. Psalm 96:9 exhorts, "Worship the LORD in the splendor of His holiness; tremble before Him, all the earth." Worship is a response to the holiness of God, characterized by humility, adoration, and a desire to honor Him in all aspects of life.

Conclusion:
The unchanging holiness of God is a cornerstone of biblical theology, shaping the understanding of His character and the believer's response to Him. It calls for a life of holiness, reverence, and worship, grounded in the recognition of God's perfect and eternal nature.