Jesus became sin

"For him who knew no sin he made to be sin on our behalf; so that in him we might become the righteousness of God" 2 Corinthians 5:21. 

The Scripture reveals us a tremendous thing that happened on the cross. Jesus was (is) God and He became a man. A sinless man. On the cross, He deliberately took off his righteousness and gave it for everybody who repents of his/her old ways and believes in Him. He also took the sins of the entire world upon Himself. Thus, on the cross He became sin. And He was punished on our behalf. 

We on the other hand, were cleansed of our sins and got the righteousness of God. This is a historic exchange between God and man, initiated by God himself. He took away our filthy sinful nature, and imparted into us His own holy nature. This becomes a reality in our lives when we look at the cross, repent of our sins and believe Jesus. The sinful nature disappears and the new one is imparted in us. What a great gift we have received from Jesus!