In Christ Is Our Righteousness

2 Corinthians 5:21 

God made him who had no sin to be sin for us, so that in him we might become the righteousness of God.

John Calvin, Institutes IV.17.2,

http://www.ccel.org/ccel/calvin/institutes.vi.xviii.html#vi.xviii-p55 

We can confidently assure ourselves, that eternal life, of which he himself is the heir, is ours, and that the kingdom of heaven, into which he has entered, can no more be taken from us than from him; on the other hand, that we cannot be condemned for our sins, from the guilt of which he absolves us, seeing he has been pleased that these should be imputed to himself as if they were his own. This is the wondrous exchange (mirifica commutatio) made by his boundless goodness. Having become with us the Son of Man, he has made us with himself sons of God. By his own descent to the earth he has prepared our ascent to heaven. Having received our mortality, he has bestowed on us his immortality. Having undertaken our weakness, he has made us strong in his strength. Having submitted to our poverty, he has transferred to us his riches. Having taken upon himself the burden of unrighteousness with which we were oppressed, he has clothed us with his righteousness. 

Martin Luther 

That is the mystery which is rich in divine grace to sinners: wherein by a wonderful exchange our sins are no longer ours but Christ’s and the righteousness of Christ not Christ’s but ours. He has emptied Himself of His righteousness that He might clothe us with it, and fill us with it. And He has taken our evils upon Himself that He might deliver us from them… in the same manner as He grieved and suffered in our sins, and was confounded, in the same manner we rejoice and glory in His righteousness.

Thomas Goodwin  Justifying Faith 

What is the gospel? Truly nothing else but that doctrine which holds forth the grace of God justifying, pardoning, and saving sinners, and Jesus Christ made righteousness to us...

John Owen, The Doctrine of Justification by Faith, Through the Imputation of the Righteousness of Christ, Explained, Confirmed, and Vindicated

He was born to us, and given to us; lived for us, and died for us; obeyed for us, and suffered for us; “…that by the obedience of one many might be made righteous.” (Romans 5:19b)

John Bunyan  Grace Abounding to the Chief of Sinners

One day as I was passing into the field…this sentence fell upon my soul. “Thy righteousness is in heaven.” I saw with the eyes of my soul Jesus Christ at God’s right hand; there, I say, was my righteousness; so that wherever I was, or whatever I was doing, God could not say of me, he (lacks) my righteousness, for that was just before him. I also saw, moreover, that it was not my good frame of heart that made my righteousness better, nor yet my bad frame that made my righteousness worse, for my righteousness was Jesus Christ himself, “The same yesterday, today, and forever” (Hebrews 13:8).

Now did my chains fall off my legs indeed. I was loosed from my afflictions and irons; my (fears) also fled away; so that from that time those dreadful scriptures of God (about the unforgivable sin) left off to trouble me; now went I also home rejoicing for the grace and love of God.

John Newton  Cardiphonia: Letters to a Nobleman

Though sin wars, it shall not reign; and though it breaks our peace, it cannot separate from his love. Nor is it inconsistent with his holiness and perfection, to manifest his favour to such poor defiled creatures, or to admit (us) to communion with himself; for (we) are not considered as in (our)selves, but as one with Jesus, to whom (we) have fled for refuge, and by whom (we) live a life of faith.

(We) are accepted in the Beloved, (we) have an Advocate with the Father, who once made an atonement for (our) sins, and ever lives to make intercession for (our) persons. Though (we) cannot fulfil the law, he has fulfilled it for (us); though the obedience of the members is defiled and imperfect, the obedience of the Head is spotless and complete; and though there is much evil in (us), there is something good, the fruit of his own gracious Spirit.

When, after a long experience of (our) own deceitful hearts, after repeated proofs of (our) weakness, willfulness, ingratitude, and insensibility, (we) find that none of these things can separate (us) from the love of God in Christ, Jesus becomes more and more precious to (our) souls. (We) love much, because much has been forgiven (us). (We) dare not ascribe anything to (our)selves, but are glad to acknowledge, that (we) must have perished if Jesus had not been (our) Saviour,  Shepherd, and Shield. When (we) were wandering he brought (us) back, when fallen he raised (us) them, when wounded he healed (us), when fainting he revived (us). In a word, some of the clearest proofs (we) have had of his excellence, have been occasioned by the mortifying proofs (we) have had of (our) own vileness.

(We) would not have known so much of him, if (we) had not known so much of (our)selves.

C.H. Spurgeon 

Mourning Christian! why weepest thou? Art thou mourning over thine own corruptions? Look to thy perfect Lord, and remember, thou art complete in him; thou art in God's sight as perfect as if thou hadst never sinned; nay, more than that, the Lord our Righteousness hath put a divine garment upon thee, so that thou hast more than the righteousness of man-thou hast the righteousness of God. O thou who art mourning by reason of inbred sin and depravity, remember, none of thy sins can condemn thee. Thou hast learned to hate sin; but thou hast learned also to know that sin is not thine-it was laid upon Christ's head. Thy standing is not in thyself-it is in Christ; thine acceptance is not in thyself, but in thy Lord; thou art as much accepted of God to-day, with all thy sinfulness, as thou wilt be when thou standest before his throne, free from all corruption.

O, I beseech thee, lay hold on this precious thought, perfection in Christ! For thou art "complete in him." With thy Saviour's garment on, thou art holy as the Holy one. "Who is he that condemneth? It is Christ that died, yea rather, that is risen again, who is even at the right hand of God, who also maketh intercession for us." (Romans 8:34) Christian, let thy heart rejoice, for thou art "accepted in the beloved"- what hast thou to fear? Let thy face ever wear a smile; live near thy Master; live in the suburbs of the Celestial City; for soon, when thy time has come, thou shalt rise up where thy Jesus sits, and reign at his right hand; and all this because the divine Lord "was made to be sin for us, who knew no sin; that we might be made the righteousness of God in him." 

        "Christ Made Sin"

See ye here the foundation-truth of Christianity, the rock on which our hopes are built. It is the only hope of a sinner, and the only true joy of the Christian, — the great transaction, the great substitution, the great lifting of sin from the sinner to the sinner’s Surety; the punishment of the Surety instead of the sinner, the pouring out of the vials of wrath, which were due to the transgressor, upon the head of his Substitute; the grandest transaction which ever took place on earth; the most wonderful sight that even hell ever beheld, and the most stupendous marvel that heaven itself ever executed, — Jesus Christ, made sin for us, that we might be made the righteousness of God in him! You scarcely need that I should explain the words when the sense is so plain. A spotless Savior stands in the room of guilty sinners. God lays upon the spotless Savior the sin of the guilty, so that he becomes, in the expressive language of the text, sin. Then he takes off from the innocent Savior his righteousness, and puts that to the account of the once-guilty sinners, so that the sinners become righteousness, — righteousness of the highest and divinest source — the righteousness of God in Christ Jesus. 

        "Christ Our Substitute"

Must it not ever be to the Christian, one of his most delightful privileges to know that altogether apart from anything that we have ever done, or can do, God looks upon his people as being righteous, nay, as being righteousness, and that despite all of the sins they have ever committed, they are accepted in him as if they had been Christ, while Christ was punished for them as if he had been sin.

Octavius Winslow  Daily Walking With God

The Lord Jesus is the life of our acceptance with God. We stand as believers in the righteousness of a living Head. Within the veil He has entered, "now to appear in the presence of God for us," (Hebrews 9:24) presenting all His people each moment complete in Himself. It is a present justification. "You are complete in Him," (Colossians 2:10) "accepted in the Beloved," (Ephesians 1:6) "justified from all things." (Acts 13:39)