Fear of God is the beginning of wisdom. Jesus teaches us we are not to be afraid of what can happen to us in this world instead we are to reverence Him. When we fear things in the world this can harm our faith. When we trust in God and stay with Him our faith grows. Faith is a great gift from God and we must protect this gift.
Luke 12: 1-7
And when great multitudes stood about him, so that they trod one upon another, he began to say to his disciples: Beware ye of the leaven of the Pharisees, which is hypocrisy.
2 For there is nothing covered, that shall not be revealed: nor hidden, that shall not be known.
3 For whatsoever things you have spoken in darkness, shall be published in the light: and that which you have spoken in the ear in the chambers, shall be preached on the housetops.
4 And I say to you, my friends: Be not afraid of them who kill the body, and after that have no more that they can do.
5 But I will shew you whom you shall fear: fear ye him, who after he hath killed, hath power to cast into hell. Yea, I say to you, fear him.
6 Are not five sparrows sold for two farthings, and not one of them is forgotten before God?
7 Yea, the very hairs of your head are all numbered. Fear not therefore: you are of more value than many sparrows.