Sixth among the conditions for the obligation of fasting: the absence of a barrier.
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The Shaykh : The absence of a barrier; the absence of a barrier is specific to women, for the barrier to fasting is either menstruation or post-natal bleeding, and this is a legal barrier. Therefore, a menstruating woman cannot fast; fasting is not obligatory upon her, and it is not valid from her, due to the saying of the Prophet (peace and blessings be upon him): Sahih al-Bukhari 1951