From sphragis; to stamp (with a signet or private mark) for security or preservation (literally or figuratively); by implication, to keep secret, to attest -- (set a, set to) seal up, stop.

see GREEK sphragis

a. for security: τί, Matthew 27:66; namely, τήν ἄβυσσον, to close it, lest Satan after being cast into it should come out; hence, the addition ἐπάνω αὐτοῦ, over him i. e. Satan, Revelation 20:3 (ἐν ᾧ —i. e. δώματι —κεραυνός ἐστιν ἐσφραγισμενος, Aeschylus Eum. 828; middle σφραγίζομαι τήν θύραν, Bel and the Dragon, , Theod.).

b. Since things sealed up are concealed (as, the contents of a letter), (σφραγίζω means, tropically, to hide (Deuteronomy 32:34), keep in silence, keep secret: τί, Revelation 10:4; Revelation 22:10 (τάς ἁμαρτίας, Daniel 9:24, Theod.; τάς ἀνομίας, Job 14:17; τούς λόγους σιγή, Stobaeus, flor. 34, 9, p. 215; θαυματα πολλά σοφή σφρηγισσατο σιγή, Norm. paraphr. evang. Ioan. 21,140).

c. in order to mark a person or thing; hence, to set a mark upon by the impress of a seal, to stamp: angels are said σφραγίζειν τινας ἐπί τῶν μετώπων, i. e. with the seal of God (see σφραγίς, c.) to stamp his servants on their foreheads as destined for eternal salvation, and by this means to confirm their hopes, Revelation 7:3, cf. Ewald at the passage; (B. D., under the words, Cuttings and Forehead); hence, οἱ εσφραγισμένοι, fourteen times in Rec. Revelation 7:4-8, four times by G L T Tr WH (δεινοισι σημαντροισιν εσφραγισμένοι, Euripides, Iph. Taur. 1372); metaphorically: τινα τῷ πνεύματι and ἐν τῷ πνεύματι, respecting God, who by the gift of the Holy Spirit indicates who are his, passive, Ephesians 1:13; Ephesians 4:30; absolutely, middle with τινα, 2 Corinthians 1:22.

d. in order to prove, confirm, or attest a thing; hence, tropically, to confirm, authenticate, place beyond doubt (a written document τῷ δακτυλίῳ, Esther 8:8): followed by ὅτι, John 3:33; τινα, to prove by one's testimony to a person that he is what he professes to be, John 6:27. Somewhat unusual is the expression σφραγισάμενος αὐτοῖς τόν καρπόν τοῦτον, when I shall have confirmed (sealed) to them this fruit (of love), meaning apparently, when I shall have given authoritative assurance that this money was collected for their use, Romans 15:28. (Compare: κατασφραγίζω.)