This will farther appear, if we consider the properties of this righteousness; and in particular, that it must not only be perfect, and therefore, such as a sinful creature cannot perform; but it must also be of infinite value, otherwise it could not give satisfaction to the infinite justice of God; and consequently cannot be performed by any other than a divine person. And it must also bear some resemblance to that debt which was due from us, inasmuch as it was designed to satisfy for the debt which he had contracted; and therefore must be performed by one who is really man. But this having been insisted on elsewhere, under the head of Christ’s Priestly office[32], we shall not farther enlarge on it; but proceed to consider, V. That our Lord Jesus Christ has wrought out this righteousness for us, as our Surety, by performing active and passive obedience; which is imputed to us for our justification. We have before considered that it is impossible that such a righteousness, as is sufficient to be the matter of our justification, should be wrought out by us in our own persons; it therefore follows; that it must be wrought out for us, by one who bears the character of a surety, and performs every thing that is necessary to our justification; such an one is our Lord Jesus Christ. In considering this head, we must, 1. Shew what we are to understand by a _surety_, since it is the righteousness of Christ, under this relation to us, which is the matter of our justification. A surety is one who submits to be charged with, and undertakes to pay a debt contracted by another, to the end that the debtor may hereby be discharged: thus the apostle Paul engages to be surety to Philemon, for Onesimus, who had fled from him, whom he had wronged or injured, and was hereby indebted to him; concerning whom, he says, _If he hath wronged thee, or oweth thee ought, put that on mine account; I, Paul, have written it with mine own hand, I will repay it_, Philem. ver. 18. And elsewhere, we read of Judah’s overture to be surety for his brother Benjamin, that he should return to his father, as a motive to induce him to give his consent that he should go with him into Egypt: _I will be surety for him; of my hand shalt thou require him: if I bring him not unto thee, and set him before thee, then let me bear the blame for ever_, Gen. xliii. 9. This is so commonly known in civil transactions of the like nature, between man and man, that it needs no farther explication; however, it may be observed, (1.) That a person’s becoming surety for another, must be a free and voluntary act: for to force any one to bind himself to pay a debt, which he has not contracted, is as much an act of injustice, as it is in any other instance to exact a debt where it is not due.