1)
What kind of touching is the Torah referring to?
1.
Rashi (citing the Sifra): It means (not touching from the outside, which is not Metamei a K'li Cheres) but being in its air-space, 1 and the Torah writes asher Yiga bo" to include Heset 2
1
Which the Sifro learns via a Gezeirah Shavah from "asher Yiga Bo" from the Pasuk in Tzav, 6:21 "Kol asher Tevushal Bo", .
2
Refer to 15:11:0.1:1.
3
See also Ba'al ha'Turim. 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.
