We need to make some important distinctions about the biblical meaning of “fearing” God. These distinctions can be helpful, but they can also be a little dangerous. When Luther struggled with that, he made this distinction, which has since become somewhat famous: He distinguished between what he called a servile fear and a filial fear.
“It is a frightening thing to fall into the hands of the living God” (Heb. 10:31). As sinful people, we have every reason to fear God’s judgment; it is part of our motivation to be reconciled with God.
Source: What Does it Mean to Fear God?