In the bible it says that only people who are in God and have the spirit of God can say or acknowledge that Jesus Christ is the Son of God. But in the bible the demons that Jesus casted out of someone acknowledged that Jesus was the son of God and they still died I don't get how they were able to say that and still die ?
The demons are aware of who Jesus is. St. James reminds us that "Even the demons believe, and tremble."
What St. Paul is talking about is that apart from the Holy Spirit is is impossible to have faith in Christ, that is, to confess that He is Lord.
There's a difference between believing in a purely intellectual way, "I believe the sky is blue", and faith in the way which Paul is using it in his letters--the kind of thing Paul is talking about is trust. The person who has faith in Christ, is the person who trusts Jesus, and His Gospel. Who says "Jesus is Lord" from a place of conviction.
Perhaps a good analogy is this:
I believe that King Charles is the reigning monarch of the United Kingdom. I believe that as a statement of fact.
I don't, however, have any trust in King Charles, or in the British Crown. It means nothing to me, I'm not a British subject, I'm an American. At the end of the day the fact that Charles is King of the UK has no importance in my life.
When St. Paul talks about saying "Jesus is Lord" is possible only by the Holy Spirit, he means it in the sense of recognizing that Jesus is Lord, and that matters. Jesus is King, Jesus is Lord, and that means something. It means Jesus has defeated the powers and principalities by His death and resurrection. It means that this declaration does something, it means my sins are forgiven, I have reconciliation with God--who I am, what I am, and what this means for me, for you, for the whole world matters, it's the most signicant thing there is.
The demons believe, and tremble--because of course they do, because the devil knows his doom is sure and time is short.
But we, who have faith, confess the Lord Jesus, Crucified and Risen, seated at the right hand of the Father--and the powers and principalities of this world are shaken, fallen, and "the kingdoms of this world are become the kingdom of our Lord and of His Christ, and He shall reign forever and ever". Jesus is Lord, and that
means something; and our lives are transformed by it.
-CryptoLutheran