This brings to mind things I read 30 years ago in William MacDonald's book TRUE DISCIPLESHIP (Kansas City, KS: Walterick, 1975), particularly this excerpt from pp.8-9:
“So likewise, whosoever he be of you that forsaketh not all that he hath, he cannot be my disciple” (Luke 14:33). This is perhaps the most unpopular of all Christ's terms of discipleship, and may well prove to be the most unpopular verse in the Bible. Clever theologians can give you a thousand reasons why it does not mean what it says, but simple disciples drink it down eagerly, assuming that the Lord Jesus knew what he was saying. What is meant by forsaking all? It means an abandonment of all one's material possessions that are not absolutely essential and that could be used in the spread of the gospel. The man who forsakes all does not become a shiftless loafer; he works hard to provide for the current necessities of his family and himself. But since the passion of his life is to advance the cause of Christ, he invests everything above current needs in the work of the Lord and leaves the future with God.It's easy to say MacDonald wasn't "mainstream" (whatever virtue attaches, or doesn't, to that) but Keller is not in any sense on the fringe of Christianity.
They aren't saying exactly the same thing, but they're pretty close. If we help feed the poor, is that spreading the gospel? Yes, according to Matthew 11:3-5. You may remember this incident; John isn't sure if Jesus is "the one who was to come"; he sends his disciples to ask Jesus. Jesus alludes to Isaiah 61:1 ("the Lord has anointed me to preach good news to the poor") in his answer to John, ending with the words "καὶ πτωχοὶ εὐαγγελίζονται" (and the poor are evangelized) -- yes, the same word is used for "the gospel."
So where does this leave you and me? Well, 30 years on, maybe I have plausible deniability for MacDonald, but then came Keller. And then this modern theologian, Stephen Colbert, who says Jesus is a liberal Democrat; I'll write more about that another day. Seriously though, how do you and I live? Do we give as much as we possibly can to the poor? Or, to lean more toward MacDonald, to spreading the gospel?
True confession: I don't. Here's a thought experiment: suppose my annual income were to suddenly drop 20% -- to what it was some years ago. What would change in my life? Would I have enough to eat, to pay the mortgage, to send my kids to college, to have dinner out occasionally, to enjoy vacations? Yes I would. Some of you would, too.
So "as much as I could possibly give" means that I could give away 20% of my gross income in addition to what we're currently giving to relief and development and evangelism, etc. So why don't I? For those of you who could live on 20% less but aren't giving away that 20%, why don't you?