Here's a great article by Tim Keller, senior pastor of Redeemer Presbyterian Church in Manhattan, NY and an adjunct professor of practical theology at Westminster Theological Seminary in Philadelphia.
The intro reads:
The original question I was asked to address was "How does our commitment to the primacy of the gospel tie into our obligation to do good to all, especially those of the household of faith, to serve as salt and light in the world, to do good to the city?" I will divide this question into two parts: (1) If we are committed to the primacy of the gospel, does the gospel itself serve as the basis and motivation for ministry to the poor? (2) If so, how then does that ministry relate to the proclamation of the gospel?
Click the intro for the rest, but brace yourself for an in-depth, gospel drenched read.