Converts to Judaism must undergo a form of this practice that encompasses the whole body within a mikvah.  
One form of this practice fell out of favor after a treatise by Maimonedes argued against Ezra's proclamation that this  practice must be done to end Keri. One form of this practice, which requires passing an object between the hands several times in a practice called negel vasser,  ends with the Asher yatzar prayer. Traditionally, hair may not be braided during another form of this practice, which must be done in order to end a time known as (*) niddah.  Converts to Judaism must undergo a form of this practice that encompasses the whole body within a mikvah.  For 10 points, name this ritual practice in Judaism that takes two forms: tevilah, which involves the whole body, and netilat yadayim, which involves just the hands, both of which require the use of water.
One form of this practice fell out of favor after a treatise by Maimonedes argued against Ezra's proclamation that this  practice must be done to end Keri.
ritual [hand] washing in water [or ritual bathing; or ablution; or immersion in water; accept equivalents of any of the preceding terms; or tevilah before read; or netilat yadayim before read; do not accept “baptism”]