According to the Mishnah on today’s daf (=page) the halakhot of shevu’at ha-eidut – the laws governing cases where a person refuses to offer testimony, swearing that he does not have information that would be useful in court – only apply to monetary cases. Thus, were someone to swear that he had no information about whether someone was a kohen or a levi, even if he was lying, the laws of shevu’at ha-eidut would not apply.
Several possible sources for this law are mentioned in the Gemara, among them the teaching of Rabbi Yossi ha-Galili, who examines the passage upon which these laws are based. In Sefer Vayikra (5:1) we find that someone who is a witness, that is, he saw an event or knows about it, will be held liable if he does not testify. Rabbi Yossi ha-Galili derives from this that these laws apply only in cases where it is possible that a witness can see without knowing or know without seeing. These criteria can only be met in monetary cases. Only there can we find cases where:
- The witness can know without seeing, e.g. in a case where the defendant admits owing money to the plaintiff, the witness can testify that he heard the admission.
- The witness can see without knowing, e.g. when he sees money being counted out and handed to someone, but he does not know why the transfer is taking place. Is he lending money? Paying off a debt? Paying for a purchase?
This latter case demands explanation, for if the witness only knows that money changed hands but does not know why the exchange was made, how can he testify?
Rashi explains that we are talking about a case where the defendant says: “if so-and-so testifies that he saw you give me money, then I will pay you.” Others object to this explanation, since in such a case the obligation stems more from the defendant’s statement than the actual testimony.
The Ramban and the R”i mi-Gash suggest that we are talking about a case where the defendant denies ever having received any money from the plaintiff, and the testimony of these witnesses will prove that he is a liar and cannot be trusted.