Is sexual intercourse permissible after a conditional oath of Zihar (e.g., 'If I approach you, you are like my mother's back'?) before expiation?

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Sexual intercourse is prohibited before the expiation (kaffarah) is completed in the case where a man says to his wife, 'If I approach you, you are upon me like my mother's back.' Imam Ahmad explicitly stated this prohibition. This ruling is used to infer the prohibition of intercourse in the preceding issue (triple divorce scenario) by implication, as the ruling for one who performs Zihar by intercourse after a triple divorce is less severe than the ruling for one who divorces three times. If intercourse occurs in this conditional Zihar scenario, the man becomes a Muzaahir (one who performs Zihar) from his wife, and the ruling of Iila' (oath of abstinence) is removed. Another interpretation from Imam Ahmad suggests this prohibition applies after the first act of intercourse, as that act itself renders him a Muzaahir, and expiation cannot precede the act of Zihar because the act is the cause, and the ruling cannot precede its cause.