Contradiction with Matthew 16:19
While Revelation 3:7 asserts that Christ holds the key of David with absolute authority, Matthew 16:19 suggests a sharing of this authority with Peter, who is given the keys of the kingdom of heaven, implying that others might also have authority to bind and loose.
Matthew 16:19: 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.
Contradiction with John 20:23
In Revelation 3:7, Christ alone holds the power to open and shut, whereas John 20:23 suggests a delegation of the power to forgive sins to the disciples, indicating a shared authority.
John 20:23: Whose soever sins ye remit, they are remitted unto them; [and] whose soever [sins] ye retain, they are retained.
Contradiction with Isaiah 22:22
Revelation 3:7 directly references Isaiah 22:22, where the prophet speaks of Eliakim holding the key of the house of David, which could contradict the exclusive application of this authority to Christ in Revelation.
Isaiah 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.