The reverse-engineering of death was something Jesus often taught on, claiming that he came to turn dead hearts (hearts of stone) into living hearts (hearts of flesh). Jesus used this term (heart of stone/flesh) almost 50 times in the Gospels, representing the inner life, the center of personality and the place where God himself resided.
What does this mean?
It means he came to give us a heart transplant.
The newness he brings to our lives isn’t just a cosmic cosmetic, but a renovation of the heart. In fact, Jesus seems to encourage his followers to develop three hearts—one of mercy (go and learn what it means to desire mercy, not sacrifice [Matthew 9.13]; one of love (a new command I give you—love one another [John 13.34]); and one of faith (I have not found such great faith in all Israel [Luke 7.9]).
That is how he makes us new. He works on us from the inside out, replacing our old selves with our new resurrection-selves.
We are no longer the same people we were before we were reunited with Christ. Now we are participants with him, and he lives in us, with us, and through us. Christ casts us as his shadows, and the more we stay in line with him, the more light we can shed in the world.
Adapted from Why God Died