Revelation 3:7-8

"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."

To the angel of the church in Philadelphia
Revelation 1:11 ... which said: "Write on a scroll what you see and send it to the seven churches: To Ephesus, Smyrna, Pergamum, Thyatira, Sardis, Philadelphia and Laodicea."

These are the words of him who is holy
Mark 1:24 "What do you want with us, Jesus of Nazareth? Have you come to destroy us? I know who you are--the Holy One of God!"
Isaiah 40:25 "To whom will you compare me? Or who is my equal?" says the Holy One.
Habakuk 3:2-3 LORD, I have heard of your fame; I stand in awe of your deeds, O LORD. Renew them in our day, in our time make them known; in wrath remember mercy. God came from Teman, the Holy One from Mount Paran. His glory covered the heavens and his praise filled the earth.

and true
1 John 5:20 We know also that the Son of God has come and has given us understanding, so that we may know him who is true. And we are in him who is true--even in his Son Jesus Christ. He is the true God and eternal life.
Revelation 6:10 They called out in a loud voice, "How long, Sovereign Lord, holy and true, until you judge the inhabitants of the earth and avenge our blood?"
Revelation 19:11 I saw heaven standing open and there before me was a white horse. whose rider is called Faithful and True. With justice he judges and makes war.

who holds the key of David
Isaiah 22:22 "I 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."
Matthew 16:19 "I will give you the keys of the kingdom of heaven; whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven."

I know your deeds
Revelation 2:2 "I know your deeds, your hard work and your perseverance. I know that you cannot tolerate wicked men, that you have tested those who claim to be apostles but are not, and have found them false." (Ephesus)

I have placed before you an open door
Acts 14:27 On arriving there, they gathered the church together and reported all that God had done through them and how he had opened the door of faith to the Gentiles.

you have kept my word and have not denied my name
Revelation 2:13 "I know where you live--where Satan has his throne. Yet you remain true to my name. You did not renounce your faith in me, even in the days of Antipas, my faithful witness, who was put to death in your city--where Satan lives." (Pergamum)

(parentheses are mine)

Scriptures taken from the Holy Bible, New International Version® NIV®, Copyright© 1973, 1978, 1984 by International Bible Society. Used by permission. All rights reserved worldwide.