Just one citation this week, but it takes a bit of explanation.
In his days Judah will be saved and Israel will live in safety. And this is the name by which he will be called: “The Lord is our righteousness.”
-- Jeremiah 23:6
Verse 6 is cited in Formula of Concord, Epitome, Article 3: Righteousness (Ep 3.1) as a central scriptural text for supporting a key idea for the Reformers following Luther--"Christ alone is our righteousness." The arguments then began after Luther's death as to how Christ is our righteousness. The argument was around the two natures of Christ. One group said Christ's righteousness comes through his divine nature, the other group said through his human nature. The conversation around this point led to the clear teaching that Christ is our righteousness because of his two natures, and that with out both together, neither nature would include us humans.
Jesus' divine righteousness is wholly in God and is too holy for us humans. Jesus' human righteousness is effective for only Jesus' humanity and cannot be parceled out to other humans. But together Jesus' righteousness as both fully God and fully human makes one person's obedience our access to God's righteousness. We stand not in our own righteousness, but in Christ's obedience, which is God's forgiveness of our sins.
If you're interested in delving into this topic, I would comment to you the Affirmative Theses of this article. What I will specifically lift up is Affirmative Thesis 2 in this article.
Accordingly, we believe, teach, and confess that our righteousness before God consists in this, that God forgives us our sins by sheer grace, without any works, merit, or worthiness of our own, in the past, at present, or in the future, that he gives us and recons to us the righteousness of Christ's obedience and that, because of this righteousness, we are accepted by God into grace and regarded as righteous.
-- Formula of Concord, Epitome, Article 3: Righteousness, Affirmative Thesis 2 (Ep 3.4)
This is the heart of what Lutherans mean when we say that Jesus is our righteousness.