What is the required form of expiation (kaffarah) for a non-Muslim subject (Dhimmi) who performs Zihar (incurring marital prohibition by comparing his wife to his mother)?

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The expiation for a Dhimmi who performs Zihar is emancipation of a slave (itq) or feeding the poor (it'am) because these acts are valid obligations upon him in other contexts, thus they are valid for expiation. Fasting (siyam) is not permissible because it is a pure act of worship, and the disbeliever is not qualified for it. Furthermore, since fasting is invalid for him outside of expiation, it is invalid within it. Emancipation is only valid if it is of a believing slave. If the Dhimmi owns or inherits a believing slave, this suffices. If not, he cannot purchase a believing slave because the contract of a disbeliever purchasing a Muslim is invalid. Therefore, the expiation must be through feeding the poor, unless he instructs a Muslim to emancipate his slave on his behalf in exchange for payment, which is valid in one report from Ahmad. If the Dhimmi converts to Islam before expiating via feeding, he is treated as a slave for this ruling, and emancipation precedes fasting, as he is in that legal status.