Jesus said, “You will know them by their fruit.”
The fruit that someone bears is representative of their heart. When someone is evil at heart, their fruit will be evil. When someone is away from God, they will not bear fruit that glorifies God. The fruit that people bear shows who they really are, and that demonstrates their passions.
A life involved in sin is a life that resembles sin. The fruit they bear is sinful in nature.
Have you seen anyone whose fruit represents the sinful nature?