Tim Keller, Gospel in Life: Grace Changes Everything (p. 25-26)
In 2 Corinthians 8 and 9, Paul wants the people to give an offering to the poor. But, he doesn’t put pressure directly on their will, saying, “I’m an apostle and this is your duty,” nor pressure directly on their emotions, telling them stories about how much the poor are suffering and how much more they have than the sufferers. Instead, Paul vividly and unforgettably says, “You know the grace of our Lord Jesus Christ, that though he was rich, yet for your sakes he became poor, so that you through his poverty might become rich” (2 Cor. 8:9). Paul brings Jesus’ salvation into the realm of money and wealth and poverty. He reminds them of the gospel. Paul is saying, “Think of Jesus’ costly grace until you are changed into generous people by the gospel in your hearts.” So the solution to stinginess is a reorientation to the generosity of Christ in the gospel, where he poured out his wealth for you. Because of the gospel you don’t have to worry about money: the cross proves God’s care for you and gives you security. Because of the gospel you don’t have to envy anyone else’s money: Jesus’ love and salvation confer on you a remarkable status—one that money cannot give you.
What makes you a sexually faithful spouse, a generous—not avaricious—person, a good parent and/or child is not just redoubled effort to follow the example of Christ. Rather, it is deepening your understanding of the salvation of Christ and living out of the changes that understanding makes in your heart—the seat of your mind, will, and emotions. Faith in the gospel restructures our motivations, our self-understanding and identity, and our view of the world. It changes our hearts. Behavioral compliance to rules without heart-change will be superficial and fleeting.