John 15:6 – If a man doesn’t remain in me, he is thrown out as a branch, and is withered; and they gather them, throw them into the fire, and they are burned.
Here we see again that there is no Christianity without Jesus. He can’t just be “a good person” to us. He must be our personal power for all of life. You can’t have a little religion and a little of the world. Jesus didn’t leave that option.
If someone tries out a relationship with Jesus and decides that it isn’t for them, if they remain separate from Him, they will eventually be burned. From other parts of the Bible, we know that there is hope for anyone who is still alive. Even if they appear to reject Jesus now, they may believe before they die.
Romans 11:22-23 – See then the goodness and severity of God. Toward those who fell, severity; but toward you, goodness, if you continue in his goodness; otherwise you also will be cut off. They also, if they don’t continue in their unbelief, will be grafted in, for God is able to graft them in again.
This passage from Romans, in context, was talking about the Jews and the ability for God to allow them to still be a part of the tree that they were cut off from. I believe that this applies to everyone. If someone starts believing in Jesus again, they are able to be put back in the right place.
It is good for them not to take this kind of risk. I believe that the “burning” that Jesus refers to is this one:
Revelation 20:10 – The devil who deceived them was thrown into the lake of fire and sulfur, where the beast and the false prophet are also. They will be tormented day and night forever and ever.
As you can see, this isn’t something anyone should risk and why it is important to carefully find out what the truth really is.