How do we forgive? Why should we forgive?  What is there about forgiveness that prevents us from taking on evil? Tim Keller's 2003 sermon at Redeemer  Presbyterian Church in NYC  is one of his best. In  this talk, Keller probes the depths of Joseph's relationship with his brothers, and explores the reasons why not forgiving someone--holding grudge, seeking retribution, etc, is a sin, and is actually being like Satan.

http://sermons2.redeemer.com/sites/sermons2.redeemer.com/files/sermons/RPC-Reconciliation.mp3