The bible says if anyone confesses Jesus is lord and believes in heart that He is raised from death by God, then he is saved.
I v met some christians believe every word of bible, but their deed behaviour is evil,
and there is another verse in bible Matt7:21-23 , those people will never enter the kingdom of God.
So, it is hard to make clear who is saved, who is unsaved, who is a real christian, who is not a christian?
It's not hard, but you basically have to accept some realities, first. We are limited in how we judge one another. We'd probably all kill each other in self-righteous indignation if we really knew the truth about each other. So our insight is limited and not absolute.
But it does exist.
Romans 10 says "believe in your heart that He is raised from the dead". That little word "believe" is not just the acceptance of a fact. That word meaning is more akin to the English word "rely".
Jesus Himself said that out of the heart come the actions (Mk 7:14-23). If someone's actions are constantly evil, never reforming, these things indicate a heart that is evil, never reforming. The wicked lie, don't they? So the wicked can put up a convincing show that "Oh, I really believe in my heart" - when they don't.
John wrote 1 John to try to help Christians recognize this character in people. It's a tough book because most translations don't give its Greek the attention it deserves. But if you look to 1 John 5, I think you can get what it's saying. Someone who's born of God believes. Someone who's born of God makes a habit of submitting to God's commands. This doesn't mean they're perfect. Far from it, if you read 1 John 1:8-10 you'll find that is not the case, we still sin. But those who do evil and
make a habit of justifying themselves aren't submitting to God's commands. That's just clear, isn't it? John thought so too. So how can we say these people actually believe? Well, we can't. Over the longterm we're gradually more and more sure that they don't believe.
Please, this isn't a "knee jerk" judgment to make about someone. Be slow in your judgments. I know times I myself didn't rush to God's protection. In this I am a stupid, slacker son; but God finally does get through to me. Don't pick just one case; we're all slackers in some sense. And we're embarrassed about not doing what we should. We're embarrassed about being creatures damaged by sin. We're all cracked pots. But someone who
makes a pattern of doing evil things, especially in defiance of God? How can he be said to be born of God? How might it be said then that he believes? At the least, such a person really shouldn't be followed in his foibles. At worst, if it keeps on & on & on: John is saying the person isn't really a believer in the first place.