Siman 124

Specifically the plaintiff can appoint a representative, as written in the previous simanim, but the defendant cannot appoint a representative. For it is understandable regarding the plaintiff, who transfers the money to the representative, and it is as if the representative is the plaintiff. But regarding the defendant, where such a transfer is not relevant, no representation is relevant. And that he should appoint a mere agent is also not within his power, because the defendant would not be able to be impudent in the presence of the plaintiff, as our Sages, of blessed memory, said: A person is not impudent in the presence of his creditor; but his agent would be impudent toward the plaintiff. Furthermore, regarding the plaintiff, there was a necessity to institute authorization and agency so that anyone should not take the money of his fellow and go away. But for the defendant, why should they institute this? Behold, the plaintiff or his agent comes to him; let him answer him himself if he has something to answer. Therefore, the defendant cannot appoint a representative or an agent to go on his behalf to beit din to answer the plaintiff while he sits in his house. And certainly when he is in beit din, he may not set up a pleader in his place, for even regarding a plaintiff this should not be done unless he is not a man of words, as written in siman 17 [Sma]. And nowadays, when it is customary that even if the plaintiff is in beit din he sets up a representative for himself, because he presumably gives him every power and authority that he has in this claim, but regarding a defendant this is not relevant [Shach]. And even with a kinyan from the defendant, it is of no avail to set up a representative [ibid.], for there is nothing upon which his kinyan can take effect, and it is a kinyan devarim. Nevertheless, if the defendant set up a representative and based on the admission of the representative the defendant was found liable, it is an admission and the defendant cannot contest this [ibid.]. And distinguished women, for whom it is not honorable to come to beit din, the scribes of the judges or attendants are sent to them and they shall plead before them; and if the plaintiff desires, he goes with them to hear their pleas from their mouths. And similarly they do for a Talmid Chacham whose Torah is his profession and he wishes to litigate before this beit din, but it is a demeaning matter for him to go to beit din and to contest together with an ignoramus. And in Yoreh Deah siman 243 it was explained what is called "his Torah is his profession." And the early authorities permitted this because of their honor, and nevertheless, they did not permit that they should set up a representative.

And all this is according to the law, but now the custom in all beit dins is that the defendant also appoints a representative, and certainly the plaintiff, whether the litigants themselves are in the beit din or whether they themselves are not in the beit din. Nevertheless, if they are not in the beit din and the beit din sees that through the representatives it is impossible to clarify the law with clarity, they send for them and they come themselves to the beit din [Urim VeTummim], and so it is proper to do.

And that which we said, that the admission of the authorized representative is an admission, this is specifically when the litigant placed words in the mouth of the authorized representative and commanded him to claim such and such, and presumably the agent performed his mission and the litigant is not believed to protest. But when he did not arrange his claims for him, but only said to him, "Go and claim for me," the litigant can afterwards protest his admission [Ktzot HaChoshen] and say that the authorized representative does not know the matter well.