How does Christ's authority manifest in opening and closing doors?

In Revelation 3:7, Christ identifies Himself as the one who has the key of David, representing His sovereign authority to grant access to salvation. This key symbolizes power and authority over spiritual realities; when He opens a door, no one can close it, and when He closes a door, no one can open it. This reassures believers that their salvation is secure in Christ, as He alone governs the access to grace and truth. Such authority underscores the idea that salvation is predestined; only those whom He has chosen can enter through the door He opens, aligning with the Reformed understanding of election and irresistible grace.