Earnest
1:
Earnest — The Spirit is the earnest of the believer’s destined inheritance (2 Cor. 1:22; 5:5; Eph. 1:14). The word thus rendered is the same as that rendered “pledge” in Gen. 38:17–20; “indeed, the Hebrew word has simply passed into the Greek and Latin languages, probably through commercial dealings with the Phoenicians, the great trading people of ancient days. Originally it meant no more than a pledge; but in common usage it came to denote that particular kind of pledge which is a part of the full price of an article paid in advance; and as it is joined with the figure of a seal when applied to the Spirit, it seems to be used by Paul in this specific sense.” The Spirit’s gracious presence and working in believers is a foretaste to them of the blessedness of heaven. God is graciously pleased to give not only pledges but foretastes of future blessedness.
Easton, M. (1996, c1897). Easton's Bible dictionary. Oak Harbor, WA: Logos Research Systems, Inc.
2:
EARNEST (Gk. arrabōn, a Semitic loan-word; Heb.‘ērāḇôn; Lat. arrha, arr(h)abo). av translation of a commercial term, probably brought W by Phoenician traders. It means, strictly, the first instalment of a gift or payment, put down as a pledge that the rest will follow later (cf. the down-payment in modern hire-purchase). Paying the earnest makes obligatory payment of the remainder.
In this sense Paul calls the gift of the Spirit an earnest of the Christian’s inheritance (Eph. 1:14; 2 Cor. 1:22; 5:5)—a guarantee (rsv), foretaste and first instalment of coming glory.
More generally, an arrabōn is any pledge or deposit, of whatever sort, given in token that a larger payment will later be made; so in lxx, Gn. 38. 17–18, 20, rendering ‘ērāḇôn.
Bibliography. O. Becker, NIDNTT 2, pp. 39f.; J. Behm, TDNT 1, pp. 475. j.i.p.
Wood, D. R. W., Wood, D. R. W., & Marshall, I. H. (1996, c1982, c1962). New Bible Dictionary. Includes index. (electronic ed. of 3rd ed.) (285). Downers Grove: InterVarsity Press.