…He said to them, "You belong to what is below, I belong to what is above. You belong to this world, but I do not belong to this world. That is why I told you that you will die in your sins. For if you do not believe that I AM, you will die in your sins."… So Jesus said (to them), "When you lift up the Son of Man, then you will realize that I AM, and that I do nothing on my own, but I say only what the Father taught me. The one who sent me is with me. He has not left me alone, because I always do what is pleasing to him." (Jn 8,21-30)
When Jesus said a sentence like this “you will die in your sin”, most of us understand that it refers only to an inward, spiritual condition, a spiritual death that takes place inside the heart and soul, and the spiritual death that takes place, at or after, physical death. This is for those who have resolutely turned against God.
And the condition for such a death is, as Jesus has said, ‘you belong to this world… you belong to what is below’. He contrasts this with, where he belongs to: ‘I belong to what is above’.
This belonging is seen in their belief in Jesus. If they do not believe that he is from above and that he belongs to what is above and that he has come from the Father, then they will die in their sin.
So, sin is, in not believing in Jesus and from where he comes. Also, the spiritual death is, in not accepting that Jesus is from the Father.
People will understand all these (that Jesus belong to what is above and he has come from the Father and he does the will of the Father) only when he is lifted up (on the cross) from the earth.
Only CROSS will teach who Jesus is.