Punishing Oneself For A Grave Sin
The punishments prescribed in sharia for crimes like adultery, thievery etc. are maximum punishments to be given to a conscious Muslim only when it is decided by the state that he deserves no linency. It is to be given by the state only when it captures the criminal. A person who has not yet been captured could do sincere repentance and mend his ways, make good any loss suffered by the other party at his hands and he should impose some sort of penalty on himself like feeding poor or giving charity etc. Regarding Kaffara of sixty fasts in case one breaks a fast intentionally , please see: Discussion 90404 __ https://youtu.be/_d0RXmLmmmY?si=a9aCRAJ4Yd_qvsVy