Witsius Explains the Righteousness of Christ

Herman Witsius
The Economy of the Covenants Between God and Man
Book II, Chapter V

XI. But we must proceed a step further, and affirm, moreover to that the obedience of Christ was accomplished by him, be believed, that it was in our room, in order thereby to obtain for us a right to eternal life. The law, which God will have secured inviolable, admits none to glory but on condition of perfect obedience, which none was ever possessed of but Christ, who bestows it freely on his own people. This is what the apostle declares, Rom. v. 16: "But the free gift of Jesus Christ is of many offenses unto justification:" that is, though we want those works, for which the reward may be due; nay, though for so many sins we may have deserved an eternal curse; nevertheless, there is something sufficient, not only for abolishing many offenses, but likewise to be the meritorious cause of righteousness; namely, the obedience of one; and it becomes ours by gratuitous gift. More clearly still, ver. 19, "For as by one man's disobedience many were made [constituted] sinners, so by the obedience of one shall many be made [constituted] righteous." The former "one man" was Adam, the root and federal head of mankind. By his disobedience, all mankind, as belonging to him, were involved in the guilt of the curse: and as he sustained the person of all, what he did amiss is accounted as done by all. The other is the "one man" Christ, who neither sinned in and with Adam, nor had the dominion of sin and death passed upon him, and who is worthy to be both lord and head, a second Adam, and the origin and source of the inheritance to be devolved on his brethren. He is possessed of an obedience, even to the whole law of God, which enjoined him to have a perfect love for the glory of his Father, and for the salvation of his brethren. By that obedience, the collective body of those who belong to him are constituted righteous; that is, are judged to have a right to eternal life, no less than if every one had performed that obedience in his own person.

*** Emphasis in original. Edited by TurretinFan (2008) to modernize spelling -- found at pages 178-79 of Volume 1 of the 1837 edition of this eminent work in systematic theology ***