Answer
The Key of David is a term found in Revelation and Isaiah. A key indicates control or authority; therefore, having the Key of David would give one control of David’s domain, i.e., Jerusalem, the City of David, and the kingdom of Israel. The fact that, in Revelation 3:7, Jesus holds this key shows that He is the fulfillment of the Davidic Covenant, the ruler of the New Jerusalem, and the Lord of the kingdom of heaven.
However, the passage in Revelation has been used inappropriately by a number of cults that ultimately descend from the Christian Identity Movement via Armstrongism. The Philadelphia Church of God, a splinter group from the Worldwide Church of God, produces a television program called Key of David.
Scriptural Usage
The Key of David is most directly referenced in Revelation 3:7, “To the angel of the church in Philadelphia write: these are the words of him who is holy and true, who holds the key of David.” The Old Testament reference is Isaiah 22:22. There, the prophet tells the palace secretary Shebna that he will be replaced by Eliakim, for God “will place on his shoulder the key to the house of David” (Isaiah 22:22). The one who holds the keys has the authority. Thus, the “key of David” implies control of David’s domain, which was promised to the Messiah in both the Old and New Testaments (Isaiah 9:7; Luke 1:32).
Cultic Usage
The television show called Key of David is hosted by Gerald Flurry, the author of a book of the same name. Flurry is founder and pastor of the Philadelphia Church of God. His interpretations of Scripture include the twisting of many biblical prophecies and a reading of many other passages as being secretly prophetic. Flurry has a special interest in Revelation 3:7-13, the letter to the church at Philadelphia (the ancient city located in modern-day Turkey). Flurry claims that the “key of David” held by Christ is “the profound understanding he wants all of us to have” (Key of David, p. 10), which will lead to special “positions of authority” (p. 11) in the New Jerusalem. Flurry claims that the letter is a vision of what Christians of our time are to do, but that “only a small percentage” (p. 8) will understand this great vision, qualify to receive the special authority, and share the throne of David with Jesus.
Another major component of Flurry’s beliefs is the claim that Great Britain and the United States of America (meaning their Caucasian, Anglo-Saxon citizens) are descended from the “lost” tribes of Israel. As Israelites (he says), we are uniquely qualified to hold authority in the Kingdom and create the spiritual Israel. This belief in Anglo-Israelism has no basis in fact.
Conclusion
Paul told Timothy to avoid “myths and endless genealogies. These promote controversies rather than God’s work—which is by faith” (1 Timothy 1:4). There is no “special knowledge” beyond the gospel itself that will aid salvation. Any claim beyond faith in the work of Jesus tears out the heart of the good news: that the just will live by faith (Romans 1:17). There is no great vision, special knowledge, or Jewish lineage needed, only faith in Christ.