Ridderbos:

How explicitly Paul speaks of “to ransom,” “to redeem,” may appear finally from a quartet of other passages where in the Greek the ordinary word for “to purchase” as a business term (agorazo, exagorazo) is employed, namely, 1Corinthians 6:20 and 7:23, where it is said: “You were bought and paid for,”43 and Galatians 3:13; 4:5, where it is said that “Christ redeemed us from the curse of the law, having become a curse for us,” and again, that he was born under the law “that he might redeem them that were under the law.” All these passages relate the salvation thus described once again with Christ’s death on the cross. When Büchsel writes: “Intentionally it is not said . . . at what cost [the Christians were bought],” this can be accepted only if it is definitely established that this price was the death of Christ 4G (cf. 1 Pet. 1:19). No other price or payment had in any case been spoken of. That we must so understand these passages–which have a paraenetic purpose and do not expressly describe the redemptive work of Christ–is clearly evident from Galatians 3:14; 4:5. There Christ’s curse death on the cross is designated as the manner ill which he has bought us. This is also the significance of Christ’s being “under the law” in Galatians 4:5.

Finally, the question arises here again as to the sense in which one will have to understand this representation of the salvation accomplished by Christ as redemption. Time and again scholars of every sort have laid stress on the fact that it is nowhere said to whom the price is paid. The main consideration here for most of them is the idea, correct in itself, that one must not think of a kind of business transaction between Christ and God, of which believers would then be the stake. To this extent one can consider it significant that it is not said that Christ paid the price to God. Yet on the other side, one should take no less care to see that the objective character of what is here called “to redeem,” “ransom,” etc., is not compromised. One runs this risk, in our view, when it is posited that there is “no question here in fact of a case at law with God,” or that Paul gives no answer to questions as to the significance of the necessity and the possibility of such a legal case with God and that, for Paul, in the cross of Christ God is not the Recipient but the One who is acting. Altogether objectionable is the notion that Paul did not consider Christ as in reality burdened with the curse of God, but speaks in Galatians 3:13 from the legalistic standpoint that he himself had rejected; in Christ it would then (on this viewpoint) appear that the curse of the law is not the curse of God and in this way the idea that God deals with men on a legalistic basis would be carried ad absurdum. The deliverance from the curse of the law would then mean only “a release from a false conception of God’s attitude.”

However much we have to guard against a pedestrian notion of “buy,” “price,” “pay,” as though the salvation Christ has accomplished were a matter of a business transaction, this does not alter the fact that the whole thought of redemption and ransom rests on the awful reality of the curse of the law (Gal. 3: 13; 4:5), a curse that one may not understand as an independent, blind force detached from God, but as the fulfillment of the divine threat against sin (Gal. 3: 14). There is here in fact, however inadequate human words may be, a case at law between God and men, both Jews and gentiles. In this Christ makes his appearance as the Mediator, who gives the ransom for all (1 Tim. 2:6). His death is the costly price in this case. Here again the great presupposition is that God himself has sent and given his own Son to that end (Gal. 4:4, 5). Just as in the passages that speak of Christ’s atoning death (see above), this is the great secret that has now been revealed, the content of the gospel. In it Christ represents God with men (1 Tim. 2:6). As the one sent of God, he takes the curse upon himself and he dies, burdened with it, in place of men on the cross. He pays the price for them, he therein unites in himself God’s saving will toward the world and his wrath against the sin of the world. In the complex of ideas concerning redemption the thought of substitution is here perhaps still clearer th an it was in the concept of Christ’s atoning death. It constitutes the fixed content of the ransom concept. For this reason the expression “became a curse for us” not only means “in our behalf,” but “in our place” as well (cf. 1 Tim. 2:6; Tit. 2:14). Although it is not thus said that Christ redeems his own from God, yet God is the one whose holy curse is executed on Christ in their place. Justice is not thrust aside, but justice is satisfied. Although we meet with no word for “satisfaction” in Paul, the idea of substitutionary satisfaction is materially present here. Salvation consists in the possibility, given by God and realized by Christ, that justice is victorious in love and love in justice. And all this one should view not in the first place as the substance of Paul’s personal experience or as the consequence of a severe, juridically conceived scheme of salvation, but as the apostolic unfolding of the meaning of the event, crossing all human expectations and calculations, of the death of Jesus Christ the Son of God. It is this eschatological fact of redemption which–in conjunction with the kerygma of the primitive church and in the light of the Old Testament, only now rightly understood – forms for Paul the propelling force for all his thoughts and causes him – not only as theologian, but as witness of revelation legitimated by Christ himself–to trace on all sides the salvation of the Lord realized in it.

Herman Ridderbos, Paul: An Outline of His Theology, (Grand Rapids, MI.: William B. Eerdmans, [1975]), 195-197.