How is the time frame determined if the sworn act involves negation and is left indefinite?

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If the oath is indefinite, such as 'If I do not strike Fulan, you are divorced three times,' the time period is determined by the husband's intention and will. The time frame becomes fixed as if it were explicitly stated, because oaths are primarily based upon intention, according to the Prophet's saying: 'Indeed, a man has only what he intended.'