In Pesachim 28a, the discussion revolves around whether a person can benefit from items that were involved in a transgression, particularly chametz during Passover. The phrase "מדויל ידו משתלם" is used to explain that if a person damages something with their hand, they are liable to pay for the damage. The context here is discussing cases of liability, similar to laws of damages, where individuals are responsible for harm they cause.