Is prayer invalidated by the minor uncovering of a free woman's body, excluding the face and hands?

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The explicit statement of Al-Khiraqi suggests that if anything of a free woman's body becomes uncovered besides her face and hands, her prayer is invalidated. This implies that even a minor uncovering invalidates the prayer, as the text treats it as 'a thing' and does not allow for leniency regarding minor exposure as is granted for a man's Awrah (intimate parts). The difficulty in guarding against minor uncovering suggests a ruling of pardon based on analogy with the minor uncovering of a man's Awrah.