In today's Gospel (Luke 12: 49-53) Jesus, the Prince of Peace, says he has come not to bring peace but division. How are we to understand this paradox? In light of what Jesus said right before this: "I have come to set the earth on fire, and how I wish it were already blazing!"
When God appeared to Moses (Exodus 3: 1-10) it was as fire, in the form of a bush that was on fire but not consumed. Yet, the fire of God does consume. According to Hebrews 12: 29, "our God is a consuming fire." What does God consume? Sin. All that is not worthy of him. All that is not holy. The fire of God is a consuming and purifying fire. We see this as well in 1 Corinthians 3: 10-17. Paul declares that we must build our lives on the one foundation--Jesus Christ. But the "stuff" of our lives, the materials with which we make our lives, have different qualities. Some of what we make of our lives is lasting and some of it is not worthy of God. At the end of our lives the fire of God's love will reveal what we've made of our lives and will purify them. As Paul puts it: "It will be revealed with fire, and the fire will test the quality of each one's work. ... But if someone's work is burned up, that one will suffer loss; the person will be saved, but only as through fire."
This is the fire Jesus came to cast on the earth--the fire of God's love. It is a fiery love that, in the words of Peter Kreeft, philosophy professor and popular author, "forgives sinners and destroys sins." For this reason, it is a love that divides, separating sinners from their sins and those who cling to their sins from those who seek to rid themselves of sin and seek God's mercy.
Ultimately, this fire is the love of the Sacred Heart of Jesus.