Repentance, atonement.
Two examples from the Narada Purana.
Drinking wine is prohibited. The penance for drinking wine is drinking clarified butter or drinking cow urine.
Anyone who steals wood, grass, meat or hides must fast for three days. Anyone who kills birds, turtles or dolphins must fast for twelve days.
Read Narada Purana here
https://www.astrojyoti.com/naradapurana.htm