Mishnah 2. This mishnah continues the list of matters in which we are more stringent with kodesh than with Terumah.
"Keilim hanigmarin b'taharah, tzerichin tevilah l'kodesh aval lo li'terumah":
Vessels go through a manufacturing process, and once that process is complete they acquire the status of a vessel - and from that moment they are susceptible to tumah. Our mishnah speaks of vessels whose manufacture was completed in a state of taharah, and even by a chaver who is careful in the laws of tumah and taharah, who took care that the vessel not become tamei and that an am ha'aretz, who is not careful about taharah, not touch it. Even so, for kodesh such vessels require immersion in a mikvah, while for Terumah this is not necessary.
The reason for the concern regarding kodesh: although the chaver guarded the vessel from becoming tamei, we are concerned that the saliva of an am ha'aretz, which is tamei, may have fallen on the vessel before its manufacture was completed. At that point the vessel was not yet susceptible to tumah, and the chaver bore no obligation to guard it, since he guarded it from tumah only from the moment it became a vessel and the laws of tumah and taharah applied to it. But we must be concerned that this saliva remained on the vessel even after its manufacture was completed, and from that point it is susceptible to tumah. This fine concern applies to kodesh alone; for Terumah we do not maintain this heightened level of vigilance.
Nevertheless, even for kodesh there is no requirement of ha'arev shemesh, and one does not wait until nightfall. We do not go that far in our stringency; immersion in a mikvah suffices, as the Gemara states.
Distinguishing between the two lists:
The Gemara teaches that although this law opens our mishnah, it actually closes the previous list: the items listed in the previous mishnah - five in number - together with this one, six in all, do not apply to kodesh alone, but also to chullin that were prepared with the purity level of kodesh. In other words, one who conducts himself with the standard of care required for kodesh even when dealing with chullin, the laws listed until now apply to him as well. The stringencies that follow, by contrast, are unique to actual kodesh, and do not apply to chullin prepared with the purity level of kodesh.
The stringencies unique to kodesh:
"Hakli metzaref mah shebetocho l'kodesh" - a vessel joins together everything within it with regard to contracting tumah, for kodesh but not for Terumah. If separate, scattered items are lying inside a vessel and a person touched one of them - with kodesh they all become tamei, since the vessel joins them together; with Terumah, however, the vessel does not join them.
"Harevi'i b'kodesh" - the fourth level of tumah. An av hatumah that touches something makes it a rishon, a rishon that touches something else makes it a sheni, and a sheni makes a shelishi. With kodesh there is even a fourth level, and it is pasul: it does not render anything else tamei, but it is itself disqualified. "V'hashelishi bi'terumah" - with Terumah the tumah spreads only until the third level, and does not reach a fourth.
"Nitmeis achas miyadav - chaverta tehorah, u'v'kodesh matbil sheteihen" - with Terumah, if one of his hands became tamei, the other remains in its taharah, and we do not say that once one hand became tamei the other did as well. But with kodesh he must immerse both of them, "shehayad metamei es chaverta b'kodesh" - and not with Terumah. And as we learned, with kodesh washing the hands from a vessel does not suffice; rather, one must place his hands into a mikvah - and for that reason both hands must be immersed.
In summary: in this mishnah we learned four additional stringencies of kodesh over Terumah: vessels whose manufacture was completed in taharah require immersion for kodesh, out of concern for the saliva of an am ha'aretz that may have fallen on them before their manufacture was completed - and even so, ha'arev shemesh is not required; a vessel joins together whatever is inside it; with kodesh there is a fourth level of tumah while with Terumah only a third; and one hand renders the other tamei with kodesh but not with Terumah. We also clarified the distinction between the lists: the items listed until now apply even to chullin prepared with the purity level of kodesh, whereas the stringencies from here onward are unique to kodesh alone.