Definition and Nature
God's decree refers to His eternal plan, by which He has sovereignly ordained everything that comes to pass. It encompasses all events in the universe, from the grandest cosmic occurrences to the minutest details of individual lives. God's decree is characterized by its immutability, wisdom, and righteousness, reflecting His perfect nature.

Biblical Foundation
The concept of God's decree is rooted in Scripture, where His sovereign will and purpose are consistently affirmed. In Isaiah 46:10, God declares, "I declare the end from the beginning, and ancient times from what is still to come. I say, ‘My purpose will stand, and all My good pleasure I will accomplish.’" This verse highlights God's ability to declare and bring about His purposes, underscoring the certainty and efficacy of His decree.

Eternal and Unchangeable
God's decree is eternal, having been established before the foundation of the world. Ephesians 1:4-5 states, "For He chose us in Him before the foundation of the world to be holy and blameless in His presence. In love He predestined us for adoption as His sons through Jesus Christ, according to the good pleasure of His will." This passage illustrates that God's decree is not reactive but proactive, established in eternity past.

Furthermore, God's decree is unchangeable. Numbers 23:19 affirms, "God is not a man, that He should lie, nor a son of man, that He should change His mind. Does He speak and not act? Does He promise and not fulfill?" This immutability assures believers that God's purposes are steadfast and reliable.

Comprehensive Scope
The scope of God's decree is all-encompassing. It includes the creation and sustenance of the universe (Colossians 1:16-17), the rise and fall of nations (Daniel 2:21), and the details of individual lives (Psalm 139:16). Proverbs 16:9 states, "A man’s heart plans his course, but the LORD determines his steps," indicating that even human decisions fall under the purview of God's sovereign plan.

Human Responsibility and Divine Sovereignty
While God's decree is comprehensive, it does not negate human responsibility. Scripture maintains a balance between divine sovereignty and human agency. Acts 2:23 speaks of Jesus being "delivered up by God’s set plan and foreknowledge," yet it also holds those who crucified Him accountable. This mystery is a profound aspect of biblical teaching, where God's sovereign will and human choices coexist without contradiction.

Purpose and Glory
The ultimate purpose of God's decree is His own glory. Romans 11:36 declares, "For from Him and through Him and to Him are all things. To Him be the glory forever! Amen." God's decree serves to manifest His attributes, such as His justice, mercy, and grace, culminating in the redemption of His people and the establishment of His eternal kingdom.

Comfort and Assurance for Believers
For believers, the doctrine of God's decree provides profound comfort and assurance. Romans 8:28 assures, "And we know that God works all things together for the good of those who love Him, who are called according to His purpose." This promise rests on the certainty of God's sovereign plan, offering hope and confidence amidst life's uncertainties.

In summary, God's decree is a foundational doctrine that underscores His sovereignty, wisdom, and purpose in all things. It invites believers to trust in His perfect plan, knowing that He is working all things for His glory and their ultimate good.