Pesachim 89B

מתני׳ הממנה עמו אחר בחלקו ⁠— רשאין בני חבורה ליתן לו את שלו, והוא אוכל משלו, והן אוכלין משלהן.

Mishnah: If one who is registered for a Paschal lamb unilaterally registers another person with him in his portion of the Paschal lamb, the other members of his group are permitted to give him, i.e., the one who included the additional person, only his portion, which was originally allotted to him. And he, the additional person, eats from his portion, i.e., the portion of he who added him; and they, the other members of the group, eat from theirs. This is because they did not agree to the inclusion of the additional person.

גמ׳ איבעיא להו: בני חבורה שהיו ידיו של אחד מהן יפות, מהו שיאמרו לו: טול חלקך וצא. מי אמרינן, מצי אמר להו: הא קבילתון. או דילמא, מצו למימר ליה: כי קבלינן ⁠— לתיקוני זביחה, אדעתא דאכלת טפי מינן ⁠— לא קבלינך.

Talmud: A dilemma was raised before the rabbis: If there is among the members of a group one of them who has fine hands, a euphemism for one who always hastens to take a large quantity of food, what is the halakha concerning whether they can say to him: Take your allotted portion to eat and leave; and don’t take any more from the other’s members portions? Do we say that he can say to them: You accepted me in the group without preconditions, and you therefore have no right to limit how much I can take now? Or perhaps they can say to him: When we accepted you, it was only for the preparation of the offering, to ensure that enough people would be registered to guarantee that the entire offering would be eaten with none left over. However, we did not accept you with the understanding that you would eat considerably more than us.

תא שמע: הממנה אחרים עמו על חלקו ⁠— רשאין [בני חבורה] ליתן לו את שלו, והוא אוכל את שלו, והן אוכלין את שלהן. מאי טעמא? לאו משום דהוי ליה כידים של אחד מהן יפות. ואי סלקא דעתך ידיו יפות מצי אמר להו קבילתון, ניהוי האי כידיו יפות!

Come and hear a resolution to the dilemma from what we learned in the Mishnah: If one who registered for a Paschal lamb registers other people with him in his portion, the other members of the group are permitted to give him only his portion. And then he and the additional people eat from his portion, and they, the other members of the group, eat from theirs. What is the reason for this? Is it not because it is comparable to a case where one of them has fine hands, because in the case of one who adds a person, he and the additional person together eat more than one portion? And if it could enter your mind to say that one with fine hands can say to them: You accepted me without preconditions, then this person, who registered an additional person to join him, should be considered as though he had fine hands, and he should be able to take a double portion. Therefore, the Mishnah rules that the group can limit the quantity of food he takes. It is apparent that the claim of one with fine hands is not accepted.