The word "seal," both substantive and verb, is often used figuratively for the act or token of authentication, confirmation, proof, security or possession. Sin is said not to be forgotten by God, but treasured and stored up with Him against the sinner, under a seal (De 32:34; Job 14:17). A lover's signet is the emblem of love as an inalienable possession (Song 8:6); an unresponsive maiden is "a spring shut up, a fountain sealed" (Song 4:12). The seal is sometimes a metaphor for secrecy. That which is beyond the comprehension of the uninitiated is said to be as "a book that is sealed" (Isa 29:11 f; compare the book with seven seals, Re 5:1 ff). Daniel is bidden to "shut up the words" of his prophecy "and seal the book, even to the time of the end," i.e. to keep his prophecy a secret till it shall be revealed (Da 12:4,9; compare Re 10:4). Elsewhere it stands for the ratification of prophecy (Da 9:24). The exact meaning of the figure is sometimes ambiguous (as in Job 33:16; Eze 28:12). In the New Testament the main ideas in the figure are those of authentication, ratification, and security. The believer in Christ is said to "set his seal to this, that God is true" (Joh 3:33), i.e. to attest the veracity of God, to stamp it with the believer's own endorsement and confirmation. The Father has sealed the Son, i.e. authenticated Him as the bestower of life-giving bread (Joh 6:27). The circumcision of Abraham was a "sign" and "seal," an outward ratification, of the righteousness of faith which he had already received while uncircumcised (Ro 4:11; compare the prayer offered at the circumcision of a child, "Blessed be He who sanctified His beloved from the womb, and put His ordinance upon his flesh, and sealed His offering with the sign of a holy covenant"; also Targum Song 38: "The seal of circumcision is in your flesh as it was sealed in the flesh of Abraham"). Paul describes his act in making over to the saints at Jerusalem the contribution of the Gentiles as having "sealed to them this fruit" (Ro 15:28); the meaning of the phrase is doubtful, but the figure seems to be based on sealing as ratifying a commercial transaction, expressing Paul's intention formally to hand over to them the fruit (of his own labors, or of spiritual blessings which through him the Gentiles had enjoyed), and to mark it as their own property. Paul's converts are the "seal," the authentic confirmation, of his apostleship (1Co 9:2). God by His Spirit indicates who are His, as the owner sets his seal on his property; and just as documents are sealed up until the proper time for opening them, so Christians are sealed up by the Holy Spirit "unto the day of redemption" (Eph 1:13; 4:30; 2Co 1:22). Ownership, security and authentication are implied in the words, "The firm foundation of God standeth, having this seal, The Lord knoweth them that are his" (2Ti 2:19). The seal of God on the foreheads of His servants (Re 7:2-4) marks them off as His own, and guarantees their eternal security, whereas those that "have not the seal of God on their foreheads" (Re 9:4) have no such guaranty.
On the analogy of the rite of circumcision (see above), the term "seal" (sphragis) was at a very early period applied to Christian baptism. But there is no sufficient ground for referring such passages as Eph 1:13; 4:30; 2Co 1:22 to the rite of baptism (as some do). The use of the metaphor in connection with baptism came after New Testament times (early instances are given in Gebhardt and Lightfoot on 2 Clem 7:6). Harnack and Hatch maintain that the name "seal" for baptism was taken from the Greek mysteries, but Anrich and Sanday-Headlam hold that it was borrowed from the Jewish view of circumcision as a seal.
See MYSTERY.
D. Miall Edwards