But of Him are ye in Christ Jesus, who of God is made unto us…righteousness… – 1 Corinthians 1:30
He is made of God unto us righteousness. This was a great want of ours, for naturally we were unrighteous, and to this hour in ourselves we are the same. Righteous we must be to be acceptable with God, but righteous we certainly are not personally, and by merit. All our righteousnesses are as filthy rags, and we are unable to stand before the great King; but there is One who says: “Take away his filthy garments from him,” and that same Deliverer, even the Lord Jesus Christ, is made of God unto us righteousness. You know how we usually speak of this as a double work. His blood cleanseth us from all guilt; by it pardon is bestowed upon the believer. He that looks to Christ is absolved from all sin completely so. Then, in addition to that cleansing, which we call pardon, there is the clothing, the arraying in the righteousness of Christ-in a word, there is justification by faith. The doctrine of imputed righteousness seems to me to be firmly established in the Word of God…Not only is Christ’s righteousness imputed to me, but it is mine actually, for Christ is mine. He who believes in Jesus, has Jesus Christ to be his own Christ, and the righteousness of Christ belongs to that believer, and is his. We are not merely imputably righteous, but the righteousness of our substitute is legally, actually, truly our righteousness. I am not now speaking of nature-that would have to do with sanctification-but I am speaking of repute before God. He reckons us to be righteous in Christ, and He does not reckon wrongly; the imputation is not a legal fiction or a charitable error. We are righteous. Depend upon it, God’s imputation is not like human imputation, which makes a thing to be what it is not: we are in Christ made actually righteous, because we are one with Him…As He is, so are we also in this respect. ~ C.H. Spurgeon
https://www.blueletterbible.org/comm/spurgeon_charles/sermons/0991.cfm