What is the ruling on divorce specified 'for the Sunnah' based on the timing of Zayd's arrival?

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If a man states, 'You are divorced if Zayd arrives, for the Sunnah,' and Zayd arrives during a time considered proper (zaman al-sunnah), the divorce occurs. If Zayd arrives during a time considered improper (zaman al-bid'ah), the divorce does not take effect until the proper time arrives. This is because he stipulated the divorce upon Zayd's arrival with a specific characteristic (the Sunnah timing), and it does not occur unless that condition is met, effectively making the ruling equivalent to him saying, 'You are divorced for the Sunnah' upon Zayd's arrival during the proper time.