The Mishna (R”H 25) tells us that beis din which sees the new moon is allowed to declare Rosh Chodesh without witnesses testifying before them. “Lo te’hey shemiya gedolah m’re’iya” – hearing testimony cannot be greater proof than seeing the event itself.
Yesh lachkor: does this mean that beis din’s first hand observation is itself a substitute for eidus, a form of eidus without the formal process of testimony, or does this mean that where beis din is a first hand observer no testimony is necessary?
The Rambam holds that a single expert mumche judge is allowed to decide cases (i.e. a beis din of three is not required), yet he also holds (Sanhedrin 5:18) that an admission, a hoda’ah, in front of such a judge is not binding. The Tur disagrees. The Rambam is problematic: if a single judge is authorized to decide cases, why can he not pasken based on a hoda’ah made in his presence?
Rav Amiel (Darkei Moshe 1:1) suggests that the single judge in this case is both the witness to the hoda’ah as well as the judge empowered to decide the case, no different than the idea of lo tehey shemia hedolah m’reiya when three judges witness the sight of the new moon and act as the court declaring rosh chodesh.
The machlokes between Rambam and Tur hinges on our chakirah. The Rambam holds lo te’hey shemiya gedolah m’re’iya is a form of eidus. Testimony requires two witnesses, not one, and therefore a single judge cannot rule based on what he sees. The Tur, however, understands lo te’hey shemiya gedolah m’re’iya to mean that no testimony is needed. Therefore, even the single judge may rule based on a hoda’ah done in his presence.
Yet some more explanation is needed. True, eidus requires the presence of two witnesses, but monetary cases can be decided based on all manner of proof, including umdena, what seems reasonable. Even if the hoda’ah in front of a single judge cannot serve as eidus, why can it not serve as at least the equal of an umdena so that he can decide the case? Rav Amiel answers this question in his Midos l’Cheker HaHalacha (11:27) based on a chiddush of the Ch. haRI”M, but bl”n I want to share with you an idea of R’ Shimon Shkop in a future post.