The bible teaches that unbelievers have a fear of death, however within my small group, some from especially rough backgrounds claim that as unbelievers they did not fear death. What is the biblical model for how fear of death changes during salvation?
Regarding your question, the Bible says that unbelievers are enslaved to the enemy through a fear of death:
The Bible's term "fear of death” refers to a deeper spiritual instinct beyond merely a simple emotion of feeling afraid. The term refers to a person’s instinctive awareness they are in jeopardy before a holy and just God Who will judge them for their sin. Satan was the cause of man’s fall, ensuring unbelievers would share His fate. Of those under the penalty of death, Satan is by far the most powerful, and therefore He is the spiritual leader of unbelievers.
Believers, on the other hand, have been redeemed by Christ, given a new spirit and indwelled by the Holy Spirit, so they are no longer accessible to Satan nor share a fear of death. Therefore, as powerful as Satan may be, his power does not extend to controlling the lives of believers, for the Spirit in us is greater than Satan.
In that sense, unbelievers are enslaved to the enemy through a fear of death (i.e., a sentence of judgment), while believers are free of that enslavement. The unbeliever's spiritual slavery leading them to obey Satan's bidding. Even in the case of suicide, the unbeliever is obeying the enemy who has convinced the person of the lie that death is a preferable outcome to life. Ironically, their fear of death leads them to obey an enemy who leads them into death.
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