Since fear is a part of my human experience this statement is a bit disconcerting. I consider myself a person of faith, but fear is something I experience. What does that say about my faith?
Looking at the story of Jairus what was he afraid of? At what point does Jesus say 'be not afraid, only believe?"
Jairus had gone to find Jesus to plead with him to come and heal his dying daughter. They are delayed by Jesus' stop to minister to the woman with the issue of blood who had reached out to touch his robe and now, as they approach Jairus house, people come from the house to inform them that the daughter has died. That is the point at which Jesus makes this statement to Jairus.
What does Jairus fear at that moment? That he is too late? That he has failed his family? The experience of losing this daughter who he loves so much? The challenge of going through such a horrificly sorrowful experience? Fear of one's own failure to be able to do the good that one knows is so needed and fear of calamity befalling one's loved ones are very understandable and common fears. Is there something about these two types of fear that makes them particularly conquerable by the application of faith?
When I fear due to my own inadequacies can I not reduce that fear by placing my trust in the Lord to be able to make up for them if not immediately, then in the long run? I can trust his grace which reduces my fear of the outcome of my failing to do all that needs doing.
When I fear calamity befalling those I love I can trust his ability to sustain them and me as we struggle through the aftermath. It does not make the sorrow less intense, but it does make it more bearable and less nightmarish.
I will still fear. Timidity, caution, and a sober sense of my own ineptitudes are part of my personality that are not going to be changed any time soon. But I think that what Jesus is saying is that, at least at times when we experience these two kinds of fear, faith in him and his ability to heal do much to sustain us and enable us to go forward with hope.