The rules and regulations of defilement are discussed at length in the Mishnah Tohorot.
Uktzim (Hebrew: עוקצים ʿUq'ṣim, stems) is the last volume (or "tractate") of the Order of Tohorot in the Mishnah.
Tohorot |
Based on Rabbi Lichtenstein's Talmud classes at Yeshivat Har Etzion, his students' notes have been edited and published as Shiurei Harav Aharon Lichtenstein on Tohorot, Zevahim, the eighth chapter of Bava Metzia, the third chapter of Bava Batra, the Ramban's pamphlet on Dinah DiGarmi, the first chapter of Pesahim, Masechet Horayot, and several critical chapters of Gittin.