Personally, I think that means fearing man over God.
In other translations it replaced fearful with "cowards who turn away from me."
Bear in mind Jesus is equating being "fearful" with having "no faith": the disciples are afraid of dying in the storm. So it's not "cowards who turn away from me"(though such would fall into the category of "fearful")
Why would God send anyone to hell
I don't believe in the common understanding of "hell" so my answer would probably be rejected by them that do. But, if we consider it for sake of argument, I'd respond, "Why would God send anyone to hell?" and whatever your answer to that would be, would be your answer to the posed question. I suppose "holy justice"?
for obeying him out of fear when Jesus said in Matthew, "don't fear man who could harm the body, but can not touch the soul; but fear God who can destroy both soul and body in hell?"
Obedience out of fear isn't obedience out of a good heart of love. It's the opposite kind of obedience: forced, and, feigned. The same way a man who has murder in his heart might not commit the act for fear of being caught and punished. His obedience is pointless, it's feigned and forced, and doesn't do anything about his murderous heart (which is the real problem).
When Jesus said that, He wasn't saying "Obey the commandments out of fear of being punished" He was talking about the disciples being hated for speaking the gospel, and not to be afraid of people, or, not to deny Him before men out of fear, as if reverencing the power of men more than that of God; He is saying, if you're going to fear, then fear the higher power in order to avoid not "speaking in the light" and "confessing before men": but He is not meaning for us to be afraid of God and "do good because you're afraid of being punished for doing wrong"
21 And the brother shall deliver up the brother to death, and the father the child: and the children shall rise up against their parents, and cause them to be put to death.
22 And ye shall be hated of all men for my name’s sake: but he that endureth to the end shall be saved.
23 But when they persecute you in this city, flee ye into another: for verily I say unto you, Ye shall not have gone over the cities of Israel, till the Son of man be come.
24 The disciple is not above his master, nor the servant above his lord.
25 It is enough for the disciple that he be as his master, and the servant as his lord. If they have called the master of the house Beelzebub, how much more shall they call them of his household?
26
Fear them not therefore: for there is nothing covered, that shall not be revealed; and hid, that shall not be known.
27 What I tell you in darkness, that speak ye in light: and what ye hear in the ear, that preach ye upon the housetops.
28 And
fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell.
29 Are not two sparrows sold for a farthing? and one of them shall not fall on the ground without your Father.
30 But the very hairs of your head are all numbered.
31
Fear ye not therefore, ye are of more value than many sparrows.
32 Whosoever therefore shall confess me before men, him will I confess also before my Father which is in heaven.
33 But whosoever shall deny me before men, him will I also deny before my Father which is in heaven.
I have read scriptures thoroughly, and God has gotten many people to repent by threatening them. Nineveh is a good example. And God warned many people of the consequences of not obeying if they continued to sin. He even showed mercy to the Israelites when they cried out to mercy after God abandoned them to be captured, and then they cried out for mercy.
That was all under the covenant of law, which "works wrath" and fear is often used to threaten people because that is what the law does, threaten people into obedience. But that is not what grace does. People who are "afraid" are that way because of the wrath of the law: but them not under law, but, under grace, are "perfected in love" and their is no "fear" or "torment" any longer, as John says concerning perfected in love:
1Jo 4:18 There is no fear in love; but perfect love casteth out fear: because fear hath torment. He that feareth is not made perfect in love.
So anyone who is "fearful" isn't "perfect in love"; and so if you're seeing anyone in scripture (or, in the world) who is "fearful" then they have not been perfected in love. Meaning, they have not come out from being under law, and, into being under grace.
And fear swept the church when Anannias and Sapphira died for lying to the Holy Spirit.
Yes, but people being fearful doesn't mean that is the means of obedience. It just means people were frightened. And if they experienced "fear" then it is manifest they weren't under grace, or, perfected in love: but were still in the perfecting/refining process under law.
And Moses also told the people of Israel not to fear when they saw the cloud on the mountain; but then he told them to use that fear to keep them from sinning.
I don't think it must work very well since people still seem to be sinning. So either fear doesn't actually work, or, no one actually fears God. But suffice it to say, these people were under law, and not, under grace. Thus the fear of wrath. Romans 4:15 Because the law worketh wrath:
and "fear" is what divides the called from the chosen:
Jud 7:3 Now therefore go to, proclaim in the ears of the people, saying, Whosoever is fearful and afraid, let him return and depart early from mount Gilead.