الباطن
هو اسمٌ من أسماء الله الحسنى، يدل على صفة (الباطنيَّةِ)؛ أي إنه...
The little water that a woman used in a secluded place to achieve complete purification from ritual impurity.
"Maa’ makluww bih" (water used in seclusion) is a little amount of water, such as that in a vessel or the like. "Used in seclusion" means that the woman uses it while being in a place where men cannot see her, out of sight, or behind curtains and the like. The woman in this definition is the adult woman who is competent for religious assignments. Complete purification means that it observes all the pillars of purification. Thus if she washed her hand only, then the water would not be called "used in seclusion". It should be used from the beginning of the purification till its end.