Responsa for Chullin 266:2
דכותה גבי כהן דיתיב אמסחתא אמאי צריך לרשום
But then in the case of the priest we must also suppose the same circumstances, that he sat by the stall; why then is it necessary to indicate [the partnership] by a sign? - Because people might say that he is only buying meat.
Shut min haShamayim
Regarding the third matter, they responded: "It is not common to trust a non-Jew." (Chullin 133b:4), and we should not rely on their testimony, and it has been said (Bava Batra 91b:6): "One who relies on them falls into their hands."
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