What kind of touching is the Torah referring to?
Rashi (citing the Sifra #1): It means (not touching from the outside, which is not Metamei a K'li Cheres, but) Heset 1 - where one moves a K'li that was touched by a Zav - which is akin to touching all of it and is therefore Metamei. 2
Sifra #2: Based on a Gezeirah Shavah from "asher Yiga bo" "Kol asher Tevushal bo" in 6:21 - it refers to the the inside of the K'li Cheres. 3 4
Refer to 15:11:0.1:1.
See Ba'al ha'Turim.
See Torah Temimah note 48.
This only applies however, if the opening of the K'li is wide enough for the Zav to place his finger inside it - to preclude earthenware jars with a narrow opening from the Din of Heset (Rashi in Shabbos, 84b). See Sifsei Chachamim.
