 Olyan argues that ritual impurity is deeply embedded into covenants, thus a religious ritual must be performed to rid the impurity from the people group.The Mishnah devotes one of its six sub-divisions, named Tohorot ("purities"), to the laws of ritual impurity.Neither the Babylonian nor the Jerusalem Talmud contains systematic commentaries to the tractates of Tohorot (except for Niddah), as these laws had little practical relevance after the destruction of the Temple.