41 Or “first installment,” “pledge,” “deposit.” Down payment. The Greek word ἀρραβών (arrabōn) denotes the first payment or first installment of money or goods which serves as a guarantee or pledge for the completion of the transaction. In the NT the term is used only figuratively of the Holy Spirit as the down payment of the blessings promised by God (it occurs later in 2 Cor 5:5, and also in Eph 1:14). In the “already—not yet” scheme of the NT the possession of the Spirit now by believers (“already”) can be viewed as a guarantee that God will give them the balance of the promised blessings in the future (“not yet”).

In other versions

and who has also put his seal on us and given us his Spirit in our hearts as a guarantee.

set his seal of ownership on us, and put his Spirit in our hearts as a deposit, guaranteeing what is to come.

He has also put his seal on us and given us the Spirit in our hearts as a down payment.

and he has identified us as his own by placing the Holy Spirit in our hearts as the first installment that guarantees everything he has promised us.

who also sealed us and gave the down payment of the Spirit in our hearts.

Who hath also sealed us, and given the earnest of the Spirit in our hearts.

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