Romans 10:2

Romans 10:2. For I bear them record that they have a zeal of God, but not according to knowledge.

Zeal is a good thing, but, like the horse without a bit, it becomes useless and even dangerous. Knowledge is the bridle in the mouth of zeal. Zeal is like fire, which may burn the house which it was intended to warm unless it be carefully governed. There must be knowledge in zeal.