Is it permissible for me to make someone swear to pay the expiation if he breaks his oath, and what is the expiation for this oath?

If a person swears that he will not speak to you if a certain action is repeated by you, and also swears that you will be responsible for his expiation (kaffarah) if he breaks his oath, then two expiations become binding upon him if the action is repeated and he breaks his oath: the first is for not speaking to you, and the second is for you not having paid the expiation if you did not do so. The expiation is by feeding ten needy persons, or clothing them, or freeing a slave. If he is unable to do that, then by fasting three days. Your paying the expiation on his behalf with his permission is permissible, but if he is able to pay the expiation himself, then it is not permissible for you to fast on his behalf.