STRONGS NT 2807: κλείς

κλείς, κλειδός, accusative κλεῖδα and κλεῖν (Luke 11:52; Revelation 3:7), accusative plural κλεῖδας and κλείς (Matthew 16:19; Revelation 1:18; cf. Kühner, § 130, i., p. 357; Winers Grammar, 65 (63), cf. Buttmann, 24 (22); (WH's Appendix, p. 157)), ἡ (from Homer down); a key. Since the keeper of the keys has the power to open and to shut, the word κλείς is figuratively used in the N. T. to denote power and authority of various kinds (cf. B. D., under the word ) viz. τοῦ φρέατος, to open or unlock the pit, Revelation 9:1, cf. ; τῆς ἀβύσσου, to shut, Revelation 20:1, cf. ; τοῦ θανάτου καί τοῦ ᾅδου, the power to bring back into life from Hades and to leave there, Revelation 1:18; τῆς γνώσεως, the ability and opportunity to obtain knowledge, Luke 11:52; τῆς βασιλείας τῶν οὐρανῶν (see βασιλεία, 3 e., p. 97b under the end), Matthew 16:19; τοῦ Δαυίδ, the power of David (who is a type of the Messiah, the second David), i. e. of receiving into the Messiah's kingdom and of excluding from it, Revelation 3:7 (apparently after Isaiah 22:22, where ἡ κλείς οἴκου Δαυίδ is given to the steward of the royal palace).