Verses with the word key in the New Testament (4 verses):

Luke 11:52
Woe unto you, lawyers! for ye have taken away the key of knowledge: ye entered not in yourselves, and them that were entering in ye hindered.

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;

Revelation 9:1
And the fifth angel sounded, and I saw a star fall from heaven unto the earth: and to him was given the key of the bottomless pit.

Revelation 20:1
And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand.