Rev 3:7, Mt 16:16-19
In the Old Testament, Isaiah prophesied that God would give the key of David to the coming Christ, so that no one could stop the works of Christ. (Isa 22:22)
Isa 22:22 And the key of the house of David will I lay upon his shoulder; so he shall open, and none shall shut; and he shall shut, and none shall open.
Jesus is the Christ with the key of David. (Revelation 3:7)
Revelation 3:7 And to the angel of the church in Philadelphia write; These things saith he that is holy, he that is true, he that hath the key of David, he that openeth, and no man shutteth; and shutteth, and no man openeth;
Jesus has given the key to preaching the gospel of the kingdom to us who believe in Jesus Christ. (Mt 16:16-19)
Mt 16:16 And Simon Peter answered and said, Thou art the Christ, the Son of the living God. 17 And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven. 18 And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it. 19 And I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven.