'Open Door' in the Bible
Now when I came to Troas for the good news of Christ, and there was an open door for me in the Lord,
And making prayer for us, that God may give us an open door for the preaching of the word, the secret of Christ, for which I am now in chains;
I know thy works: behold, I have set before thee an open door, and no man can shut it: for thou hast a little strength, and hast kept my word, and hast not denied my name.
After these [things] I looked, and behold, an open door in heaven, and the former voice that I had heard like a trumpet speaking with me was saying, "Come up here and I will show you [the things] which must take place after these [things]."