For when something ahead of you frightens you, or fear is simply what you wake up with.
After these things the word of the LORD came unto Abram in a vision, saying, Fear not, Abram: I am thy shield, and thy exceeding great reward.
The first "fear not" in the Bible, spoken to Abram after a raid and before a promise he has no evidence for. It answers a particular worry, that he is childless and exposed, with presence and protection rather than with an explanation.
And Moses said unto the people, Fear ye not, stand still, and see the salvation of the LORD, which he will shew to you to day: for the Egyptians whom ye have seen to day, ye shall see them again no more for ever. The LORD shall fight for you, and ye shall hold your peace.
Moses says this with Egypt's chariots behind the people and the sea in front. It is not advice for steadying the nerves; it is an instruction to stop running and watch, given at a moment when there was nowhere left to run.
Have not I commanded thee? Be strong and of a good courage; be not afraid, neither be thou dismayed: for the LORD thy God is with thee whithersoever thou goest.
Spoken to Joshua as he takes command after Moses dies, facing a war he did not choose. The courage commanded is tied to one specific thing, that God is with him wherever he goes, and not to any assurance that the campaign will be short.
Fear thou not; for I am with thee: be not dismayed; for I am thy God: I will strengthen thee; yea, I will help thee; yea, I will uphold thee with the right hand of my righteousness.
Addressed to Israel as a nation among frightening empires, not first to an individual. The verbs are the substance of it: God says he is present, strengthens, helps, upholds. What is promised is company through the threat, not the removal of it.
God is our refuge and strength, a very present help in trouble. Therefore will not we fear, though the earth be removed, and though the mountains be carried into the midst of the sea; Though the waters thereof roar and be troubled, though the mountains shake with the swelling thereof. Selah.
A psalm of refuge that names the worst thing it can picture, mountains sliding into the sea, and says the refuge holds even then. It does not claim the ground will stay still. It claims there is somewhere to stand while it moves.
What time I am afraid, I will trust in thee. In God I will praise his word, in God I have put my trust; I will not fear what flesh can do unto me.
"What time I am afraid, I will trust in thee" concedes the fear rather than denying it, so trust here is something done while still afraid. The limit the psalm draws is specific: on what flesh can do, which is a real limit and not an unlimited one.
And I say unto you my friends, Be not afraid of them that kill the body, and after that have no more that they can do. But I will forewarn you whom ye shall fear: Fear him, which after he hath killed hath power to cast into hell; yea, I say unto you, Fear him. Are not five sparrows sold for two farthings, and not one of them is forgotten before God? But even the very hairs of your head are all numbered. Fear not therefore: ye are of more value than many sparrows.
Jesus tells followers in actual danger that the worst a persecutor can do has an end, then turns to sparrows sold for pennies and counted hairs. The comfort is not that nothing will happen to them, which he assumes may, but that nothing happens unnoticed.
The fear of the LORD is the beginning of wisdom: and the knowledge of the holy is understanding.
A different sense of the word, included so the two are not confused. The fear of the LORD in the Hebrew Scriptures means awe and a reckoning with God, the posture wisdom begins from. It is not the dread that the "fear not" passages answer.