This is the meaning of expiation in this specific action, and expiation may be in other than this, which is to protect oneself from taking revenge on you for the wrongdoings you committed. There are people for whom expiation is a cover for the wrongdoings that befall him if you go against him to seek it out for the desire of the lustful soul. He is infallible with this concealment, so there is no ruling on him for violating him. These two meanings are different from the first, and among people are those who combine all of that. In this world there are all three of these rulings, and in the hereafter there are two in particular, which is the first concealment, and the concealment is that he does not suffer retaliation