This is how Jesus described himself when he spoke to the church in Philadelphia in the Book of Revelation.
Rev 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. What he opens no one can shut, and what he shuts no one can open.
This expression appears in the story of Eliakim, who was the palace administrator during the time of Hezekiah (King of Judah).
Isa 22:20“In that day I will summon my servant, Eliakim) son of Hilkiah.Isa 22:21I will clothe him with your robe and fasten your sash around him and hand your authority over to him. He will be a father to those who live in Jerusalem and to the people of Judah.Isa 22:22I will place on his shoulder the key to the house of David; what he opens no one can shut, and what he shuts no one can open.Isa 22:23I will drive him like a peg into a firm place; he will be a seat of honor for the house of his father.Isa 22:24All the glory of his family will hang on him: its offspring and its offshoots—all the small containers, from the bowls to all the jars.Isa 22:25“In that day,” declares the Lord Almighty, “the peg driven into the firm place will give way; it will be sheared off and will fall, and the load hanging on it will be cut down.” For the Lord has spoken.
In other words, this symbolizes the key given to a steward who faithfully manages what they have received from God (finances, gifts, etc.).