These are the things for which the interest is collected from someone in this world and the principal remains for the world to come: idol worship, sexual prohibitions, and the shedding of blood; and gossip is equal to them all. A meritorious deed has principal and has interest as it says in the Torah: (Isaiah 3:10
) "Hail the just person for it is good for them, for they shall eat the fruits of their works etc".
For a transgression there is capital but there is not interest as it says in the Torah (Isaiah 3:11
) "Woe to the wicked one, it is bad for them; as their hands have dealt so it shall be done for them". If so how do I make sense of the verse "They will eat the fruit of their ways, etc." (Proverbs 1:31
). For a transgression that yields results there is interest, for one that doesn't yield results there is not interest. [Edited for gender neutrality]