فإن جامع المعتكف ليلا أو نهارا: بطل اعتكافه.
Translation: If the person in iʿtikāf has sexual intercourse by night or day, the iʿtikāf is invalidated.
Fasting restrictions apply during daylight, but the prohibition of intercourse in iʿtikāf applies both day and night. Finishing the daily fast does not lift this separate restriction.
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Bab al-Iʿtikaf: Rules, Restrictions, Invalidation and Vows
فإن جامع المعتكف ليلا أو نهارا: بطل اعتكافه.
Translation: If the person in iʿtikāf has sexual intercourse by night or day, the iʿtikāf is invalidated.
Fasting restrictions apply during daylight, but the prohibition of intercourse in iʿtikāf applies both day and night. Finishing the daily fast does not lift this separate restriction.