Tehorot - Order of Tractates

Order of Tractates

The traditional reasoning for the order of the tractates (according to Rambam) is as follows. Kelim is first as it introduces the levels of impurity, and dictates to which object the various impurities apply at all. Oholot follows because it outlines the most serious type of impurity. Negaim follows because it is next in severity and because, like a corpse, a metzorah transmits tent-inpurity. Parah follows as it outlines the purification for the severe impurities already dealt with. The next stage is lesser impurities (Tohorot) and their method of purification which is immersion (Mikvaot). Niddah follows as it is also a lesser impurity but it has the extra feature of applying to only a portion of people (i.e. to women). Makshirin, Zavim and Tevul Tom follow Niddah based on Scriptural order. The next stage down is impurities that are Rabbinic only (Yadaim). Finally, Uktzin is last as it is restricted and has no Scriptural source, the laws being derived from the reasoning of the Sages.

There is a Babylonian Gemara on only Niddah. This is because most of the other laws of purity do not apply when the Temple is not in existence. The Talmud Yerushalmi (Jerusalem Talmud) only covers four chapters of Niddah.