A pool or bath of clear water, immersion in which renders ritually clean a person who become ritually unclean through contact with the dead (Num. 19) or any other defiling object or through an unclean flux from the body (Lev. 15) and especially a menstruant.
It is similarly used for vessels (Num 31: 22- 23). At the present day the chief use of the mikveh is for the menstruant. since the laws of ritual impurity no longer apply after the destruction of the Temple. Nevertheless, since according to the halakhah the contracting of marital relations while the wife is in the state of niddah is a particularly severe offense, punishable by karet, and according to one opinion in the Talmud ( not however accepted as halakhah), that a child born of such a union is a mamzer, the rabbis insisted meticulous adherence to the laws of immersion in a mikveh before his mother could resume marital relations.
They are also obligatory for the immersion of proselytes, as part of the ceremony of conversion. In addition immersion in the mikveh is still practiced by various groups as an aid to spiritually, particularly on the eve of the Sabbath and festivals, especially the Day of Atonement (see Ablution) and the customs still obtains, in accordance with Numbers 31: 22 - 23 to immerse new vessels and utensils purchased from non-Jews.

Mikveh
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