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James 2 
14What good is it, dear brothers and sisters, if you say you have faith but don’t show it by your actions? Can that kind of faith save anyone? Suppose you see a brother or sister who has no food or clothing, 16and you say, “Good-bye and have a good day; stay warm and eat well”—but then you don’t give that person any food or clothing. What good does that do? 17So you see, faith by itself isn’t enough. Unless it produces good deeds, it is dead and useless.

We need to act upon what we know, or else it won't do any good.