In Bible times, a seal was an engraved stamp for impressing a design onto a soft, yielding material such as damp clay, e.g. Job 38.14, which was then dried or baked. These seals had some kind of graphic device or lettering, carrying a sign, figure, letter, or word as an identifiable emblem of their owner. The lump of stamped or "sealed" clay was often attached to a document or other object by strings. The seal itself could be hung by a string or chain from the arm or neck, or used as a signet ring, often worn in those days on the little finger of right hand. The word seal also came to mean the impressed material with its mark left by the seal.
When used in connection with a document, the seal gave it official validity, serving as the equivalent of the modern signature; in fact no document was regarded as authentic without its seal. Indeed, the Latin word from which our word "seal" derives also gives us our words sign, signet, and signature. The seal also gave accreditation to weights and measures; the guarantee of the genuineness of articles sealed in containers; proof of ownership of property, or protection of houses or graves against violation.
"Signed, sealed and delivered" is an expression we still use for properly finishing and handing over a thing, and today we also still speak of a "seal of approval". The idea of a signet ring also survives today, but not for its original purpose!
Summarising, we see that sealing with a seal was a mark of accreditation, attestation, confirmation, guarantee, identification, possession, protection, security or validation, representing the person and power of its owner. When used figuratively, the seal had therefore a wide meaning, and the context decides the particular significance.
Then the word "earnest" in the New Testament is similar to the word "pledge" in the Old Testament. It was the deposit, part- or down-payment given for an item by the purchaser as a token of later full payment, to prove his or her seriousness and sincerity in the undertaking. Used figuratively the earnest is a pledge, guarantee, promise, surety, or token whereby the person giving it proves his or her good intentions with regard to future promised action. Therefore, to the person to whom it is given it represents a present, tangible proof of future fulfilment. It is also interesting to note that the word translated "earnest" in the New Testament is the equivalent of the word for an engagement ring in modern Greek, and an engagement ring is a present promise of future fulfilment.
As we will see, both seal and earnest are used in the New Testament with reference to the Holy Spirit and the believer.
Old Testament background
A seal and an earnest (pledge) appear together first in connection with an unhappy incident in the life of Judah (Gen 38.17-18). When asked for a pledge by Tamar, Judah offered his seal (signet, AV - Gen 38.18,25). A very striking example of the (mis)use of a seal in the Old Testament was when Jezebel "wrote letters in Ahab's name, and sealed them with his seal" (1 Kings 21.8). For other examples of sealing documents see also Deuteronomy 32.34; Nehemiah 9.38, 10.1; Esther 3.12, 8.8,10; Song of Solomon 8.6; Isaiah 8.16; Jeremiah 22.24, 32.10,11,44. Sometimes the impression material is used figuratively as the heart (Song 8.6), meaning the leaving of an imprint, thus having the name and likeness impressed on the heart.
The seal could be attached to some other object, such as when "a stone was brought, and laid upon the mouth of the den; and the king sealed it with his own signet, and with the signet of his lords; that the purpose might not be changed concerning Daniel" (Dan 6.17). The signet ring of an Eastern monarch was the sign of delegated authority; thus the Lord said of Zerubbabel that He would "make thee as a signet" (Hag 2.23).
The same skill that went into the engraving of a seal or signet ring was used to good effect for the high priest's attire as shown in Exodus, for the names of the tribes of Israel were engraved on the precious stones for the high priest's ephod, as the engravings of a seal or signet (8.11,21; 39.14, JND), and as an attachment to his headgear "they made the thin plate, the holy diadem, of pure gold, and wrote on it with the writing of the engravings of a seal, Holiness to Jehovah!" (28.36; 39.30, JND). Bezaleel was divinely gifted in such things - "I have filled him with the spirit of God, in wisdom, and in understanding, and in knowledge, and in all manner of workmanshipin cutting of stones, to set them" (31.2 5). Natural talent was not sufficient of itself, but into the hearts of those who were already wise-hearted the Lord put wisdom, "that they may make all that I have commanded" (v.6). The same is true today, and we should look to the same Lord to supplement any natural talent for His use with His wisdom.
New Testament usage
The idea of the seal is sometimes used literally in the Gospels. When the stone placed across the entrance of Joseph's new, rock-hewn tomb was sealed, this was probably by means of a cord stretched across it, fixed to the outside of the tomb on both sides by lumps of wet clay. The official Roman seal was then impressed upon the clay (Mt 27.66; cp. Dan 6.17), and woe betide anyone daring to break the seals! As someone has said, "They did their best to prevent theft and the resurrection, but they overreached themselves and provided additional witness to the fact of the empty tomb and the resurrection of Jesus". Who would roll away the "very great" stone (Mk 16.4) with its attendant soldiers and attached seal?
The word seal is otherwise used metaphorically. For instance, the idea of attestation or authentication given by the seal is taken up in the Gospels: "He that hath received [Jesus'] testimony hath set to his seal that God is true" (Jn 3.33). The person who accepts the witness of the Lord Jesus asserts that He spoke the message of God, i.e. they set their seal to His testimony. Anyone today who believes in the Lord Jesus Christ has equally attested and declared that God is true.
Then, God has Himself equally testified about the authenticity of His Son (see Jn 6.27, which says literally, "For this one the Father sealed", i.e. set His seal [of approval] on). It is not clear to what John referred when saying that the Father set his seal of approval on the Son. Some think it was done at his baptism when the Holy Spirit came upon him and the Father spoke to him (cf. 5.37), but this alone would not exhaust the idea of divine authentication, since His miracles were also from the Father. As Nicodemus could say, "Thou art a teacher come from God: for no man can do these miracles that thou doest, except God be with him" (Jn 3.2). Then we read that "God anointed Jesus of Nazareth with the Holy Ghost and with power: who went about doing good, and healing all that were oppressed of the devil; for God was with him" (Acts 10.38), then, "Ye men of Israel, hear these words; Jesus of Nazareth, a man approved of God among you by miracles and wonders and signs, which God did by him in the midst of you, as ye yourselves also know" (Acts 2.22), and lastly, "I have greater witness than that of John: for the works which the Father hath given me to finish, the same works that I do, bear witness of me, that the Father hath sent me" (Jn 5.36).
To be continued.