Tim Keller discussing the term “poor in spirit” in his newest book, “Generous Justice: How God’s Grace Makes Us Just”:
It means to see that you are deeply in debt before God, and you have no ability to even begin to redeem yourself. God’s free generosity to you, at infinite cost to him, was the only thing that saved you. What if, however, you aren’t poor in spirit? That would mean you don’t believe you are so sinful, morally bankrupt, and lost that only free grace can possibly save you. You may find the classic Christian doctrines about humanity’s deep sin and lostness to be too harsh. On the contrary, you believe that God owes you some things – he ought to answer your prayers and to bless you for the many good things you’ve done. Even though the Bible doesn’t use the term, by inference we can say that you are “middle-class in spirit.” You feel that you’ve earned a certain standing with God through your hard work. You also may believe that the success and the resources you have are primarily due to your own industry and energy.
My experience as a pastor has been that those who are middle-class in spirit tend to be indifferent to the poor, but people who come to grasp the gospel of grace and become spiritually poor find their hearts gravitating toward the materially poor. To the degree that the gospel shapes your self-image, you will identify with those in need. You will see their tattered clothes and think: “All my righteousness is a filthy rag, but in Christ we can be clothed in his robes of righteousness.” When you come upon those who are economically poor, you cannot say to them, “Pull yourself up by your bootstraps!” because you certainly did not do that spiritually. Jesus intervened for you. And you cannot say, “I won’t help you because you got yourself into this mess,” since God came to earth, moved into your spiritually poor neighborhood, as it were, and helped you even though your spiritual problems were your own fault. In other words, when Christians who understand the gospel see a poor person, they realize they are looking into a mirror. Their hearts must go out to him or her without an ounce of superiority or indifference.