(2.) He that engages to be surety for another must be in a capacity to pay the debt, otherwise he is unjust to the creditor, as well as brings ruin upon himself: therefore it is said, _Be not thou one of them that strike hands, or of them that are sureties for debts, if thou hast nothing to pay; why should he take away the bed from under thee?_ Prov. xxiii. 26, 27. (3.) He who engages to be surety for another, is supposed not to have contracted the debt himself; and therefore the creditor must have no demands upon him, as being involved together with the debtor, and so becoming engaged antecedent to his being surety: nevertheless, he is deemed, in the eye of the law, consequent thereunto, to stand in the debtor’s room, and to be charged with his debt, and equally obliged to the payment thereof, as though he had contracted it, especially if the creditor be resolved to exact the payment of him, rather than of the original debtor[33]. (4.) As debts are of different kinds, so the obligation of a surety agreeably thereunto admits of different circumstances: thus there are pecuniary debts resulting from those dealings or contracts which pass between man and man in civil affairs; and there are debts of service or obedience; as also debts of punishment, as has been before observed, for crimes committed; in all which cases, as the nature of the debt differs, so there are some things peculiar in the nature of suretyship for it. In pecuniary debts the creditor is obliged to accept of payment at the hand of any one, who at the request of the debtor is willing to discharge the debt which he has contracted, especially, if what he pays be his own; but in debts of service or punishment, when the surety offers himself to perform of suffer what was due from another, the creditor is at his liberty to accept of, or refuse satisfaction from him, but might insist on the payment of the debt by him in his own person, from whom it was due. 2. Christ was such a surety for us, or substituted in our room, with a design to pay the debt which was due to the justice of God from us. Here, that we may assume the ideas of a surety but now-mentioned, and apply them to Christ, as our surety, let it be considered; (1.) That what he did and suffered for us was free and voluntary; this appears from his readiness to engage therein, expressed by his saying, _Lo, I come to do thy will_, Heb. x. 9. And therefore whatever he suffered for us did not infer the least injustice in God that inflicted it[34]. (2.) He was able to pay the debt, so that there was not the least injury offered to the justice of God by his undertaking. This is evident, from his being God incarnate; and therefore in one nature he was able to do and suffer whatever was demanded of us, and in the other nature to add an infinite value to what he performed therein.