John Calvin Commentary Luke 12:49

"I came to cast fire upon the earth; and what do I desire, if it is already kindled?" — Luke 12:49 (ASV)

I am come to send fire on the earth. From these concluding words, it can easily be inferred that this was one of Christ's latest discourses and is not related by Luke in its proper place. But the meaning is that Christ has introduced into the world the utmost confusion, as if He intended to mingle heaven and earth.

The gospel is metaphorically compared to fire, because it violently changes the state of things. The disciples had falsely imagined that the kingdom of God would come while they were at ease and asleep. Christ declares, on the contrary, that there must first be a dreadful conflagration to kindle the world.

And as some beginnings of it were even then appearing, Christ encourages the disciples by this very consideration: that they already feel the power of the gospel. “When great commotions,” He says, “already begin to kindle, this is so far from being a reason for you to tremble, that it is rather a ground for strong confidence; and, for My part, I rejoice that this fruit of My labors is visible.”

In the same way, all ministers of the gospel should apply this to themselves, so that when there are troubles in the world, they may be more diligently engaged in their duty.

It is also important to observe that the same fire of doctrine, when it burns on all sides, consumes chaff and straw but purifies silver and gold.