אֲבָל בַּלַּיְלָה אֲפִילּוּ שְׁלֹשָׁה כּוֹתְבִין וְאֵין עוֹשִׂין דִּין מַאי טַעְמָא דְּהָווּ לְהוּ עֵדִים וְאֵין עֵד נַעֲשֶׂה דַּיָּין אֲמַר לֵיהּ אִין הָכִי נָמֵי קָאָמֵינָא: but if they came at night, even if three men came to visit the sick person, they may write the will and sign it as witnesses but they may not act in judgment. What is the reason that they may not act in judgment the next day? It is because they are already witnesses to the will of the deceased, and there is a principle that a witness cannot become a judge, i.e., one who acts as a witness in a particular matter cannot become a judge with regard to that same matter? Rabba bar Ḥanina said to Abaye: Yes, it is indeed so; this is what I was saying.
אִיתְּמַר קִנְיָן עַד אֵימָתַי חוֹזֵר רַבָּה אָמַר כׇּל זְמַן שֶׁיּוֹשְׁבִין רַב יוֹסֵף אָמַר כׇּל זְמַן שֶׁעוֹסְקִין בְּאוֹתוֹ עִנְיָן § After mentioning Rav Yehuda’s ruling the Gemara cites a related dispute. It was stated: With regard to a transaction, until when may one of the parties renege on the transaction? Rabba says: As long as they are seated in the same location they may renege on the transaction. Rav Yosef says: As long as they are dealing with that matter, i.e., they are still discussing that transaction, they may renege on it.
אָמַר רַב יוֹסֵף כְּווֹתִי דִּידִי מִסְתַּבְּרָא דְּאָמַר רַב יְהוּדָה שְׁלֹשָׁה שֶׁנִּכְנְסוּ לְבַקֵּר אֶת הַחוֹלֶה רָצוּ כּוֹתְבִין רָצוּ עוֹשִׂין דִּין וְאִי סָלְקָא דַּעְתָּךְ כׇּל זְמַן שֶׁיּוֹשְׁבִין לֵיחוּשׁ דִּלְמָא הֲדַר בֵּיהּ Rav Yosef said: It stands to reason in accordance with my opinion, as Rav Yehuda says: In a case where there were three men who entered a room to visit a sick person and the sick person desires to write a will in order to distribute his property following his death, if the visitors wish to do so they may write his will and sign it as witnesses. And if they wish, they may act in judgment. And if it enters your mind that one may renege on a deal as long as they are seated in the same location, then let us be concerned that perhaps he will renege on his decision. How can the visitors act in judgment in a case where the matter has not been resolved, as the sick person may still change his mind?
אָמַר רַב אָשֵׁי אַמְרִיתַהּ לִשְׁמַעְתָּא קַמֵּיהּ דְּרַב כָּהֲנָא וּלְרַב יוֹסֵף מִי נִיחָא וְלֵיחוּשׁ דִּלְמָא הָדַר בֵּיהּ אֶלָּא מַאי אִית לָךְ לְמֵימַר דִּיסְלִיקוּ Rav Ashi said: I stated this halakha before Rav Kahana and I asked him: And according to the opinion of Rav Yosef, does it work out well? But even according to his opinion there should be a concern that perhaps he will renege on his decision, as Rav Yosef holds that one may renege on a transaction as long as the two parties are still dealing with that matter. Rather, what have you to say? That according to Rav Yosef, Rav Yehuda’s ruling applies where they withdrew