These people believe but are not saved.
Matt 7:21-24 “Not everyone who says to Me, ‘Lord, Lord,’ will enter the kingdom of heaven, but the one who does the will of My Father who is in heaven will enter. Many will say to Me on that day, ‘Lord, Lord, did we not prophesy in Your name, and in Your name cast out demons, and in Your name perform many miracles?’ And then I will declare to them, ‘I never knew you; leave Me, you who practice lawlessness.’
“Therefore, everyone who hears these words of Mine, and acts on them, will be like a wise man who built his house on the rock
Some versions of this say "you who break Gods Law" instead of "you who practice lawlessness"
Those who believe but continue in sin are in big trouble.
1 Cor 6:9-10 says “Don’t you realize that those who do wrong will not inherit the Kingdom of God? Don’t fool yourselves. Those who indulge in sexual sin, or who worship idols, or commit adultery, or are male prostitutes, or practice homosexuality, or are thieves, or greedy people, or drunkards, or are abusive, or cheat people—none of these will inherit the Kingdom of God.”
Luke 6:46 says, “Now why do you call Me, ‘Lord, Lord,’ and do not do what I say?” It then continues to verse 49. It says to act on Jesus' words. It shows what it is like for someone to act and for those that don’t. Those who act will have a solid foundation. While those who do not act will be washed away with their weak foundation.
Jesus said these verses when people could see Him in the flesh. So, they fully believed He was real but not all were saved. Simple belief will not save you. Even the demons believe.
Romans 8:12-14 also says, "So then, brothers and sisters, we are under obligation, not to the flesh, to live according to the flesh, for if you are living in accord with the flesh, you are going to die; but if by the Spirit you are putting to death the deeds of the body, you will live. For all who are being led by the Spirit of God, these are sons and daughters of God." So, believe and repent. Do not live according to the flesh. Simply believing will not save you. That is a false teaching that you need to stop spreading. Even the demons believe. So, do not fool yourself.
Stopping sin is a result of real belief, remorse and contrition. God desires a broken and contrite heart.
Those who continue in sin are like this:
If I were to hit you and then say sorry, you would accept my apology. Then if I was to hit you the following day and then say sorry, you would begin to wonder if I was truly sorry. Then the day after this, I did the same thing, you would realise that I was not truly sorry. My words may say one thing, but my actions show another. What you act out is what you truly believe. If you are truly broken and contrite, then there will be a change in you. That is why the bible says that we are given a new heart and new mind. One that obeys Him. "I will give you a new heart and a new mind. I will take away your stubborn heart of stone and give you an obedient heart." Eze 36:26
Continuing in sin is like a person who enjoys nailing the nail into Jesus' left hand and then says sorry. Then he goes to the right hand and enjoys the sin again and puts in another nail. Then he says sorry. He continues to the left foot and repeats the same thing. And lastly, the right foot. But then he restarts back at the left hand again and puts in another nail.
Belief by itself will not save you. Act upon your belief. Even the demons believe.
1 John 3:3 "And everyone who has this hope set on Him purifies himself, just as He is pure." So, leave your sin.