When Jesus talks about fire, he means in the first place his own Passion, which was a Passion of love and was therefore a fire; the new burning bush, which burns and is not consumed; a fire that is to be handed on.
Jesus does not come to make us comfortable; rather he sets fire to the earth; he brings the great living fire of divine love, which is what the Holy Spirit is, a fire that burns. In an apocryphal saying of Jesus that has been transmitted by Origen, he says: Whoever comes close to me comes close to the fire. Whoever comes close to him, accordingly, must be prepared to be burned.
It burns, yet this is not a destructive fire but one that makes things bright and pure and free and grand. Being a Christian, then, is daring to entrust oneself to this burning fire. Christ is the one who brings peace. And I would say that this is the saying that is preeminent and determinative.
But we only properly comprehend this peace that Christ brings if we do not understand it in banal fashion as a way of cheating one's way out of pain, or out of the truth and the conflicts that truth brings with it.
If the Church simply aims to avoid conflict, merely to ensure that no disturbances arise anywhere, then her real message can no longer make any impact. For this message is in fact there precisely in order to conflict with our behavior, to tear man out of his life of lies and to bring clarity and truth. Truth does not come cheap. It makes demands, and it also burns.
Pope Benedict XVI