Toharot, Chapter Four, Mishnah Six
Our mishnah deals with spittle that is found and whether or not one must treat it as impure lest it have come from a zav or a nidah, both of whose spit is impure.
1) Two kinds spittle, one of which was [possibly] unclean and the other was definitely clean:
a) [Terumah] is to be held in suspense if [touched by one who] touched or carried or shifted [one of the two kinds of spittle] while they were in a private domain;
b) Or who touched one of them in a public domain while it was still moist;
c) Or who carried it whether it was moist or dry.
2) If there was but one [kind of possibly] unclean spittle and a person touched, carried or shifted it in a public domain, terumah is burned on account of it;
a) And one does not even need to say that this is the case if it was in a private domain.
Section one: In this section there are two kinds of spittle, meaning that they came from two different people. The first kind of spittle was simply found; we don’t know who it came from. The second kind of spittle was definitely clean. The mishnah now goes on to describe various scenarios where a person might have been defiled by the unknown spittle.
If a person touched, carried or shifted one of them while in a private domain, but he is not sure which spittle it was, then if he subsequently touched terumah, the terumah is “suspended.” As we have seen, this means that it is not burned, as it would be if it was impure, but neither can it be eaten. This matches the opinion of the sages in yesterday’s mishnah, that in cases of doubtful impurity in the private domain terumah is suspended.
Terumah is also suspended if the person touched the spittle in the public domain and it stuck to his body because the spittle was still moist. The sages considered a person’s body to be like a private domain and the spittle attached to him is treated as doubtful impurity found in the private domain.
Similarly, if the person carries it, the spittle is considered to be in the private domain because a person treated like a private domain.
Section two: However, if there is only one kind of spittle and he is sure that he had contact with it, or carried it or shifted it, then the rule reverts to the general principle found in mishnah five. The terumah is burned even if this occurs in the public domain, all the more so if it occurs in the private domain, where the rule is stricter.