That the righteousness of the law might be fulfilled in us,.... By the righteousness of the law, is not meant the righteousness of the ceremonial law, though that was fulfilled by Christ; but of the moral law, which requires holiness of nature, righteousness of life, and death in case of disobedience; active righteousness, or obedience to the precepts of the law, is designed here.
This is what the law requires; obedience to the commands of it is properly righteousness; and by Christ's obedience to it we are made righteous, and this gives the title to eternal life: now this is said to be "fulfilled in us"; this is not fulfilled by us in our own persons, nor can it be; could it, where would be the weakness of the law?
man might then be justified by it, and so the grace of God, and the righteousness of Christ, must be set aside: there never was any mere man that could fulfil it; for obedience to it must not only be performed perfectly, but with intenseness of mind and spirit; a man must be sinless in thought, word, and deed; and this would be to put man upon a level with Adam in a state of innocence, and the angels in heaven: nor is this to be understood of any righteousness inherent in man; internal holiness is never called the righteousness of the law; and could it be thought to be righteousness, yet it can never be reckoned the whole righteousness of the law: and though it is a fruit of Christ's death, it is the work of the Spirit, and is neither the whole, nor any part of our justification: but this is to be understood of the righteousness of the law fulfilled by Christ, and imputed to us; Christ has fulfilled the whole righteousness of the law, all the requirements of it; this he has done in the room and stead of his people; and is imputed to them, by virtue of a federal union between him and them, he being the head, and they his members; and the law being fulfilled by him, it is reckoned all one as it was fulfilled in, or if by them; and hence they are personally, perfectly, and legally justified; and this is the end of Christ's being sent, of sin being laid on him, and condemned in him.