Definition and Scope:
Royal authority in the biblical context refers to the divinely sanctioned power and responsibility bestowed upon kings and rulers to govern and lead the people of Israel and, by extension, other nations. This authority is often depicted as a reflection of God's ultimate sovereignty and is characterized by both privilege and accountability.

Biblical Foundations:
The concept of royal authority is deeply rooted in the Old Testament, where God establishes kingship as a means to lead His people. The first explicit mention of a king in Israel is found in Deuteronomy 17:14-20, where God provides guidelines for the establishment of a monarchy. The king is to be chosen by God, and his authority is to be exercised in accordance with divine law: "When you enter the land the LORD your God is giving you and have taken possession of it and settled in it, and you say, 'Let us set a king over us like all the nations around us,' you are to appoint over yourselves the king the LORD your God will choose" (Deuteronomy 17:14-15).

The Role of Kingship:
The role of the king in Israel was multifaceted, encompassing leadership in warfare, administration of justice, and spiritual oversight. The king was expected to be a model of covenant faithfulness, leading the nation in adherence to God's commandments. The king's authority was not absolute; he was subject to the law of God and the prophetic word. This is exemplified in the reign of King David, who, despite his failings, is described as a man after God's own heart (1 Samuel 13:14).

Divine Appointment and Anointing:
Royal authority was often conferred through anointing, symbolizing the king's consecration to God's service. The anointing of Saul by the prophet Samuel marks the beginning of the monarchy in Israel (1 Samuel 10:1). Similarly, David's anointing signifies God's choice and blessing upon his reign (1 Samuel 16:13).

The Davidic Covenant:
A significant aspect of royal authority is the Davidic Covenant, in which God promises David that his throne will be established forever (2 Samuel 7:12-16). This covenant underscores the enduring nature of royal authority as part of God's redemptive plan, ultimately fulfilled in Jesus Christ, the "Son of David" (Matthew 1:1).

The Ideal King:
The Old Testament prophets often spoke of an ideal king who would embody perfect justice and righteousness. Isaiah prophesies about a future ruler: "For to us a child is born, to us a son is given, and the government will be upon His shoulders. And He will be called Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace" (Isaiah 9:6). This messianic expectation finds its fulfillment in the New Testament with the coming of Jesus Christ, who claims all authority in heaven and on earth (Matthew 28:18).

New Testament Perspective:
In the New Testament, royal authority is redefined through the person and work of Jesus Christ. Jesus, as the King of Kings, exercises authority not through political power but through sacrificial love and servanthood. His kingdom is not of this world (John 18:36), and His authority is demonstrated through His teachings, miracles, and ultimately, His resurrection.

Accountability and Judgment:
Kings in the Bible were held accountable for their exercise of authority. The narratives of Saul, David, Solomon, and subsequent kings illustrate the consequences of obedience and disobedience to God's commands. The prophets served as God's messengers, calling kings to repentance and warning of judgment for unfaithfulness.

Conclusion:
Royal authority in the Bible is a complex and multifaceted concept, reflecting both the privileges and responsibilities of leadership under God's sovereign rule. It serves as a type and shadow of the ultimate authority of Christ, who reigns eternally as the righteous King.