Revelation chapter three, verses seven and eight, says:
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. I know your deeds. See, I have placed before you an open door that no one can shut. I know that you have little strength, yet you have kept my word and have not denied my name.
With these verses Jesus starts his letter to another of the seven churches, the church at Philadelphia. The writer at thetrumpet.org suggests that the term 'key of David' is a metaphor for Salvation through Christ, meaning that Salvation given to us by Jesus cannot be taken from us by anyone; no one can close our door to heaven. Conversely, it also means that no one else can open the door of Salvation for us but Christ himself. This verse about the 'key of David' is also a reference to another Bible verse, Isaiah 22:22, which speaks about the key of David in almost identical terms.
If you want to accept Salvation from Christ here are some resources:
A Prayer for Salvation from Christ:
Lord Jesus, I confess my sins and ask for your forgiveness. Please come into my heart as my Lord and Savior. Take complete control of my life and help me to walk in Your footsteps daily by the power of the Holy Spirit. Thank you Lord for saving me and for answering my prayer.
A more detailed step by step process:
https://www.wikihow.com/Accept-Jesus-Into-Your-Life
