What is the evidence for the maximum length of menses being fifteen days, and what is the maximum length of tuhr (purity)?

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Check below answers in case you are looking for other related questions:
If the bleeding lasts for more than 15 days is it still regarded as menstruation, and can she fast?
How can a woman determine that her period has ended so that she can pray?

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Related Answers:
She did ‘Umrah and prayed when she was menstruating
Brownish discharge that appears before menses
She got a yellowish discharge after forty days of nifaas; can she pray and fast?
If the bleeding lasts for more than 15 days is it still regarded as menstruation, and can she fast?
How can a woman determine that her period has ended so that she can pray?

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