Paul Tripp on the New Heart
It is not enough for Paul to say that the death of Christ made him new. He says that when he died, the old Paul was not replaced with a new and improved version of Paul, but with Christ himself! He’s not simply saying that the new Paul is better at controlling the sin in his heart. He is saying that where sin once controlled, Christ now rules! Our hearts, once under the domination of sin, are now the dwelling place of Christ, the ultimate source of righteousness, wisdom, grace, power, and love.
My heart is new, because Christ lives there. My heart is alive, because Christ lives there to give it life. My heart can respond to life in new ways because it is no longer dominated by sin, but liberated by the gracious rule of Christ. That is why I have the potential for amazing change and growth in my heart and life.
—How People Change, 150.