QUESTION: The Mishnah teaches that when a person pledges to donate an amount of a particular commodity that is equal to his own weight, he brings his weight of the commodity that he specified.

However, a person's weight fluctuates during the day, depending on whether he is before or after a meal. When, then, do we assess his weight? The SHITAH MEKUBETZES (#3) in the name of the ROSH answers that it is logical for him to donate the amount equal to his weight at the time he made the vow.

The CHAFETZ CHAIM in ZEVACH TODAH asks why is this case not judged like a case in which a person says, "Dami Alai" ("I shall donate my monetary value to Hekdesh")? Such a person must give to Hekdesh what he is worth at the time the donation is given, and not at the time that the vow was made (Erchin 18a)!

(a) RASHI explains the reason why one who says "Dami Alai" must give to Hekdesh what he is worth at the time the donation is given: that is the only way to assess him. We cannot retroactively assess him for his value at the time that he made the vow. TOSFOS (18a, DH she'Yiten) explains that the requirement to give his value as of the moment that he gives the donation is a Gezeiras ha'Kasuv, a Torah injunction with no apparent reason.

Accordingly, in the case of the Gemara here, Rashi may understand that since it is possible to find out how much he weighed at the time of day that he made his vow (by weighing him at a similar time on another day), we require him to give the weight that he weighed at the time of his vow. (ZEVACH TODAH)

According to Tosfos, however, why does a vow of "Mishkali Alai" differ from "Dami Alai"? Why do we not assess his value at the time that he gives the donation?

(b) The TZAFNAS PANE'ACH (Erchin 2:3) writes that although when a person says "Dami Alai" he must be assessed by ten people (Erchin 19b, RASHI DH Umdena), this is not necessary when a person promises to give his weight to Hekdesh. In such a case, he does not need an assessment of ten people. It is only when a person's worth is being assessed that the Torah requires that he be evaluated by ten, just as the value of land, which has no set or standard value, must be evaluated by ten ("Adam Hukash l'Karka," as the Gemara says in Sanhedrin 16a). Determining a person's weight involves no more than clarifying a detail, and no subjective evaluation is necessary.

Accordingly, it may be suggested that the Gezeiras ha'Kasuv that applies to "Dami Alai" (which requires that the person's monetary value be assessed based on the time of the giving of the donation) applies only when an assessment is required. A vow of "Mishkali Alai," which involves merely clarifying the person's weight, is different and can be based on the time of the actual vow. The same approach may be suggested according to Rashi's understanding; since there is no Halachic requirement to evaluate a person's weight, it can be determined by an informed estimate. (Z. Wainstein)

OPINIONS: The Gemara asks what a person's obligation is when he pledges, "Yeshivasi Alai" -- "my 'sitting' is upon me [to give to Hekdesh]." What does this statement mean? What might the person be obligated to give?

(a) TOSFOS (19a) gives three explanations for the Gemara's question. In his first explanation, he explains the Gemara's question as follows: Does the person who makes the vow intend to donate a staff of gold that cannot be bent, which stands at the same height as his height while he is sitting, or does he intend to give a flexible staff of gold, which is the length of his full height? The person denotes his full, flexible height with the word "Yeshivasi," since his height is bent while he is seated.

(b) In his second explanation, Tosfos suggests that the Gemara is asking whether the one who makes the vow intends to donate a staff which is as long as the distance from the top of his head until his waist (where he sits), or a staff the length of his full height while he is sitting.

(c) In his third explanation, Tosfos suggests that the Gemara is asking whether the one who makes the vow intends to donate a staff the length of his height while seated, or a staff that occupies the same area as he occupies when seated.

QUESTION: In the Mishnah (19a) and Beraisa (19b), Rebbi Yehudah describes how the weight of one's hand is calculated in order to assess the amount of gold or silver that one must give when he pledged, "The [amount of gold or silver equal to the] weight of my hand is upon me [to give to Hekdesh]." Rebbi Yehudah explains that he places his hand into a cask full of water and displace the amount of water equal to the volume of his hand. He then takes the flesh, bones, and sinews of a donkey that weigh the same as his hand and places them into the cask until the water reaches the top. He then weighs that donkey flesh and gives the amount of gold or silver that is equal to the weight of that donkey flesh.

If he first must weigh the donkey flesh in order to ascertain the amount of flesh that corresponds to the weight of his hand in order to know how much flesh to put into the cask of water, then why does he have to put the flesh into the cask of water at all? The purpose of putting his hand, and then the donkey flesh, into the water is to discern the weight of donkey flesh that corresponds to the weight of his hand. If, however, he already knows the weight of his hand (such that he is able to separate an amount of donkey flesh equal to that weight), then why does he need to use the water-displacement procedure? (TOSFOS 19b, DH v'Shokel)

(a) TOSFOS answers that when the Mishnah says "v'Nosen" -- "and he places [the donkey flesh into the cask of water]," it means "she'Nosen" -- "which he places...." The Mishnah is not saying, "And he weighs the flesh of a donkey and he places it into the cask," but rather the Mishnah is saying, "And he weighs the flesh of a donkey which he has placed into the cask." He does not weigh the flesh first, because he does not know how much his hand weighs. It is the water-displacement procedure that enables him to ascertain the weight of his hand.

(b) Tosfos answers in the name of the RI that when the Mishnah says that he must weigh the flesh, it does not mean that he weighs it in order to take a quantity that equals the weight of his hand. He does not know the weight of his hand; he is using the water-displacement procedure to find out how much his hand weighs. Rather, the Mishnah means that he must weigh the donkey flesh before he places it into the water because it will increase in weight as a result of absorbing some of the water in the cask. If he places the flesh into the cask before he weighs it, then when he removes the flesh that made the water rise to its original level and weighs it, the flesh will weigh more than the actual weight of his hand that displaced the water, due to the water absorbed in it, and he will end up giving more than he is obligated to give.

QUESTION: Rava rules that the monetary value of a hand is assessed in the same way that a hand is assessed for purposes of Nezikin (compensation for damages). Abaye disagrees and rules that the value of a hand is assessed by comparing the value of a slave that can work with both hands to that of a slave who can work with only one hand (because his other hand has a different owner and may not be used for work for this owner).

The RAMBAM (Hilchos Erchin 2:3) rules in accordance with Abaye. This ruling, however, does not seem to be consistent with the rule that whenever Rava and Abaye disagree, the Halachah follows the ruling of Rava (except for six cases in which the Halachah follows the ruling of Abaye; see Bava Metzia 21b). Why does the Rambam rule like Abaye?

ANSWER: Perhaps the Rambam understands that after Abaye explained to Rava his logic, Rava conceded to Abaye in this case. (Although Rava later discusses the Halachah in a case in which a person was assessed for Nezikin and then made a vow to give the monetary value of his hand to Hekdesh, it must be that Rava raised that question before he retracted his opinion and conceded to Abaye.)