Our Scripture reading today is 2 Corinthians 5:20-21.
Verse 21, "For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him."
The perfect Lamb of God lovingly and willingly laid down His life in order to make it possible for sinful man to be forgiven.  Jesus Christ became sin for every sinner.  What he did not become was a sinner.  "Even His becoming sin was a righteous act of love, not an act of sin."  He stood in the place of guilty sinners like you and me.  
When we come to Jesus Christ for salvation there is an amazing exchange that takes place.  He takes our sin debt (We could never pay it.) and give us His righteousness. (We could never deserve it.)  Our righteousness is not in and of ourselves.  “The righteousness which Adam had in the garden was perfect, but it was the righteousness of man: ours is the righteousness of God.” (Spurgeon)
Hallelujah, What a Saviour!!