I am not in agreement with everything Spear says regarding the atonement, however, some of his comments here are insightful and instructive.

The Atonement and the Penalty of the Law¹

Samuel T. Spear,

Thirdly, it is further admitted that the figure of paying a debt is a very inadequate and defective exhibition of the work of Christ. “At the same time, we shall be careful not to push this similitude (of debtor and creditor) to an unlawful extreme, nor to represent the satisfaction of Christ as tallying in all respects with that which is made in human transactions.” “But pecuniary transactions, we not only admit but insist, can furnish no perfect parallel to the mysterious transaction of saving sinners.” “This does not make redemption a commercial transaction, nor imply that there are not essential points of diversity between acquiring by money, and acquiring by blood. Hence our second remark is, that if Dr Beman will take up any elementary work on theology, he will find the distinction between pecuniary and penal satisfaction clearly pointed out, and the satisfaction of Christ shown to be of the latter, and not of the former kind.” Thus it appears that the figure of paying, a debt by a surety, is defective; and that a “penal satisfaction only is meant by it. The analogy between sin and a debt is very remote, and equally so that between a “penal satisfaction” and the payment of a debt. It is by unduly pressing this analogy, that errors have arisen in respect to the atonement. “The supposition of an exact and perfect resemblance between the atonement and the payment of a pecuniary debt, might lead us to deny the full extent of the provision made by the death of Christ for the salvation of mankind; or it might lead us to believe that all men will finally be saved; or what is a still more shocking error, to believe that sinners are under no obligation to obey the divine law, and cannot be justly required to endure its penalty.” Strictly speaking, the atonement pays no debt; neither is Christ a surety for a literal debtor…

Fifthly, the term surety is applied but once to the Saviour in the New Testament, and not at all in the Old. “By so much was Jesus made a surety of a better testament” Heb. 9: 22. In this chapter the apostle shows the superiority of Christ’s Priesthood over that of the Mosaic system. He refers to the solemnity of His appointment: Thou art a priest forever, after the order of Melchisedec.” He then reasons–“And inasmuch as not without an oath he was made priest, * * * By so much was Jesus made a surety of a better testament.” The apostle does not say, surety of the elect undertaking to pay their “boundless debt,” but “surety of a better testament“–meaning the gospel dispensation placed in contrast with the Mosaic, which he speaks of a being disannulled. In precisely what sense Christ is a surety, does not appear, except from the word itself. The term means a bondsman, a security, one who pledges himself for another. What the apostle says is, that Christ is the bondsman, so to speak, of the Covenant, the “better testament.” To continue the figure, (for it is plainly a metaphor.) He signs the covenant and seals it with His own blood–stands pledged for it. The commercial idea of’ a debtor and a creditor, and of Christ as stipulating to pay to the latter the debt of the former, is almost infinitely removed from what the apostle said. True, “the Redeemer is expressly called a surety; but of what? “Of a better testament,” and not the elect undertaking to pay their “boundless debt.”

Sixthly, the commercial metaphors of the Bible used to describe the work of Christ, have no analogy to the idea of a debt paid by a surety. Christians are said to be bought with a price–redeemed with the precious blood of the Saviour. These are confessedly metaphorical expressions, though teaching the delivery of His people from the curse of the law by the death of Christ. In the language of metaphor His blood was the price of their redemption; by it they have been released from the curse of a violated law. But these metaphors are not analogous to the proper idea of a surety. This is a very different metaphor. A surety does not redeem him for whom he is surety; he pays no price for him; he simply pays his debt, or stands pledged for it. The metaphor of a redeemer respects the persons of the redeemed; that of a surety respects not the persons, but merely a pecuniary liability. Hence when Christ is said to redeem us, and His people to be bought with a price, the idea of a surety is not at all contained in the figure. It is, therefore, illogical, not authorized by the Scriptures, to say that Christ is a surety stipulating to pay the “boundless debt” of the elect, and then refer to tho terms price, bought, redeemed, ransom, in confirmation of this proposition. The terms do not imply the idea figuratively–much less, literally.

Finally, the similitude between the payment of a debt by a surety, and the work of Christ as a Saviour, besides being not at all Scriptural, is in almost all respects defective. A debt infers no fault or crime; a debtor as such is no violator of law; but Christ’s work is in behalf of sinners, and on account of sin. A debt infers no penal exposure ; but sinners are in danger of eternal damnation. A creditor is not a public, but a private person: he may remit the debt without satisfaction, and is bound to cancel it when paid by a surety. God is not the sinner’s creditor, but his lawgiver; and the work of Christ in his behalf has reference to the government of a sovereign ruler. In it are obstacles to the sinner’s pardon, which have not the faintest analogy to the relation of a creditor. A debt is ferable; a surety may assume it and pay it. Sin is not transferable; it belongs inalienably to the being who committed it. Neither is the ill-desert of sin transferable:² and if, as the reviewer of Beman on Atonement declares, and as we firmly believe, “ill-desert * * * is the ground of just liability to punishment,” then this “liability” is not transferable. Hence, to quote the words of President Dwight, “All that, in this case, can be done by a substitute of whatever character, is to render it not improper for the lawgiver to pardon the transgressor.” Samuel T. Spear, “The Atonement and the Penalty of the Law,” The Biblical Repository 3^rd Series 6, no. 1 (1850), 138-140.

Credit to Tony.

¹I have not reproduced the footnotes. All Italics original to Spear.
²On this, see Charles Hodge, Systematic Theology, 2:476-477.