2 Corinthians 7:10 For sadness in a godly way makes for repentance to salvation that is not to be regretted; but the sadness of the world produces death.

What is the sadness of the world? The cross reference points to Genesis 4:13 where God has just punished Cain for killing his brother. Is Cain repentant? No, he says “My punishment for error is too great to carry.” Cain was not sorry for having killed his brother, but only for being punished for it. This is the sadness of the world as opposed to sadness in a godly way – sadness for the sin committed.