“God made him who had no sin to be sin for us, so that in him we might become the righteousness of God.” 2 Corinthians 5:21
Hebrews 3:13 “Encourage one another every day, as long as it is called “today,” that none of you may be hardened by sin’s deceitfulness.”
What is God’s righteousness? I’m persuaded that to is to see people through God's eyes. And what do we see? We see people who are so exceedingly valuable to him that the only matching price tag God could put on them was the precious blood of his son, Jesus. And how precious is the blood of Christ? We know that it is incommensurably precious — that is to say — it is beyond all standards of measurement. Hence there is no limit to the value God places on us.
So to be the righteousness of God, is to live increasingly seeing others through God's eyes. That in turn leads us to always seek to deeply respect and magnify the their value in everything we think, say, and do.
Conversely, unrighteousness is living indifferent to other people’s value to God. Horrifyingly, when we believe no one matters to God, and come to the place where we no longer seek to self-sacrificially help or protect anyone, we are on the road to the place of the dead — a hard heart. And eventually no matter how many exit ramps God gives us to make our way back, we will ignore them all.