Augustine of Hippo

"The fear of the Lord is the hope of courage." When you fear the punishment that is threatened, you learn to love the reward that is promised; and thus through fear of punishment you keep on leading a good life, and by leading a good life you acquire a good conscience, so that finally through a good conscience you don't fear any punishment. Therefore, learn how to fear, if you don't want to be afraid.

Sermon 348:1 ↗

Gregory the Dialogist

In the way of God fear produces strength; as Solomon witnesses, who says, "In the fear of the Lord is strong confidence." For 'strong confidence' is said 'to be in the fear of the Lord,' in that, in truth, our mind so much the more valorously sets at nought all the terrors of temporal vicissitudes, the more thoroughly that it submits itself in fear to the Author of those same temporal things. …

Morals on the Book of Job, Book 5.33 ↗

Bede

In the fear of the Lord is strong confidence, etc. The fear of the Lord provides the confidence of strength, because indeed our mind more valiantly despises the terrors of temporal things as much as it submits itself more truly to their creator through strength. …

Commentary on Proverbs ↗