James 2:19 Updated American Standard Version (UASV)
19 You believe that God is one. You do well; the demons also believe, and shudder.
The Bible difficulty here is that the Bible says that for one to receive salvation, they must “Believe in the Lord Jesus, and you will be saved.” (Ac 16:31) Also, John3:16 says, “everyone trusting in him [Jesus] will not be destroyed but have eternal life.” (John 3:16). Other translations read, “whoever believes in him should not perish but have eternal life.” (ESV, NASB, LEB, CSB, et.) The apostle Paul says salvation comes “to the one who does not work, but believes in him.” (Rom. 4:5) If these verses are the case, all that one must do is believe in Jesus, this one will receive salvation, why not the demons, James said, “the demons also believe”?
The answer lies within the word “believe.” Believe, faith, Trust in: (Gr. pisteuo) If pisteuo is followed by the Greek preposition eis, (“into, in, among,” accusative case), it is generally rendered “trusting in” or “trust in.” (John 3:16, 36; 12:36; 14:1) The grammatical construction of the Greek verb pisteuo “believe” followed by the Greek preposition eis “into” in the accusative gives us the sense of having faith into Jesus, putting faith in, trusting in Jesus.
Why Is the Greek verb pisteuo (faith, Believe, trust in) rendered differently at times?
|John 3:16 Updated American Standard Version (UASV)
16 For God so loved the world that he gave his only-begotten Son, in order that everyone trusting in him will not be destroyed but have eternal life.
|John 3:36 Updated American Standard Version (UASV)
36 The one trusting in the Son has eternal life, but the one who disobeys the Son will not see life, but the wrath of God remains on him.
A Grammar of New Testament Greek series, by James Moulton, says, “The importance of the difference between mere belief … and personal trust.” Both these senses can be conveyed using the Greek word pisteuo. The context helps us to identify the different senses of the meaning of pisteuo. Then again, we also have the different grammatical constructions that also convey what the Bible author had meant by his use of the word. When pisteuo is simply followed by a noun in the dative case, it is merely rendered as “believe,” such as the chief priest and elders response to Jesus at Matthew 21:25, “If we say, ‘From heaven,’ he will say to us, ‘Why then did you not believe him?’ However, in Romans 4:3 we have pisteuo follow by a noun in the dative in the Updated American Standard Version, yet it is rendered “For what does the Scripture say? “Abraham put faith in God, and it was credited to him as righteousness.” (The ASV, RSV, ESV, NASB, and others have “Abraham believed God”)
If pisteuo is followed by the Greek preposition epi, “on,” it can be rendered “believe in” or believe on.” At Matthew 27:42, it reads, “we will believe in him [i.e., Jesus].” At Acts 16:31, it reads “And they said, Believe on the Lord Jesus Christ, and thou shalt be saved …” (KJV, UASV similarly) What is the difference between “believing in Jesus” and “believing on Jesus”? Believing in Jesus is a merely acknowledging that he exists while believing on Jesus is to accept absolutely, having no doubt or uncertainty, trusting in, putting faith in or trust in, exercising faith in the Lord Jesus Christ.
If pisteuo is followed by the Greek preposition eis, (“into, in, among,” accusative case), it is generally rendered “trusting in” or “trust in.” (John 3:16, 36; 12:36; 14:1) The grammatical construction of the Greek verb pisteuo “believe” followed by the Greek preposition eis “into” in the accusative gives us the sense of having faith into Jesus, putting faith in, trusting in Jesus.
You see, we are not talking about a simple belief in but rather exercise a saving kind of faith. Therefore, James is showing his readers that a mere belief in and of itself is not truly a genuine faith, even though it might impact one emotionally. Only genuine faith the produces good works can save. (Jam. 2:17) Yes, it is faith alone that saves us, this kind of faith will produce good works. We are not saved by works (Eph. 2:8-9), but genuine faith will produce good works, or it is not genuine faith. The demons are spirit persons, who have actually seen God and know very well that he exists, and that he is the Creator of all things, including them. Because they know and believe this to be true, it does impact them, namely, they shudder, as they know that their end is destruction. (Mark 1:24; 2 Pet. 2:4; Jude 6) Therefore, the demons will not be saved because they do not have saving kind of faith, which leads to good works. Rather, they are in opposition to God. Think of this interesting point, though, none of the demons are atheists or agnostics. These positions are only found among skeptical, doubting humans that say they must see God in order to accept or believe that he is real.
 James Moulton, A Grammar of New Testament Greek, Vol. 1: Prolegomena (London, England: T & T Clark International, 2006), 68.