I Chronicles 10:13 So Saul died for his transgression which he committed against the LORD, even against the word of the LORD, which he kept not, and also for asking counsel of one that had a familiar spirit, to enquire of it;
Salvation is forever. Salvation is by grace, totally undeserved and unearned. But to take from these truths the idea that sin does not have consequences would be a foolish and arrogant stance to take.
Saul died for his transgression. Doesn’t say he went to hell. He died. When we sin there will be consequences. If you are His child you will live a different life or be chastised.
This is not talking about petty things that church and religion often like to talk about. It is gross, obvious sin. Saul deliberately did what he knew that the Lord clearly had taught him not to do. He did it willfully and intentionally.
He disobeyed God. He chose to go his own way instead of following what he knew that God wanted.
Please never get the idea that grace means forget God. Grace means love Him more. Seek Him more!