Ketubot 24B

הכא נמי בשכלי אומנותו בידו.

Here too, it is referring to a case where the second donkey driver comes with the tools of his trade in his hand, clearly indicating that he too came to sell his produce. Therefore, when the other driver praises his produce, there is room for concern that there was collusion and that in the next city their roles will be reversed. However, when there is no proof of collusion, the Rabbis were not concerned.

והיכא אתמר דרבי חמא בר עוקבא ⁠— אהא, דתנן: הקדר שהניח קדירותיו וירד לשתות (מים מן היאור) ⁠— הפנימיות טהורות, והחיצונות טמאות.

The Talmud asks: And where is the solution of R' Ḥama bar Ukva stated? It is stated concerning that which we learned in a Mishnah (Teharot 7:1): In the case of a potter who fashioned his vessels in ritual purity, and abandoned his pots, and descended to drink water from the river, there is concern that in his absence ritually impure people came into contact with his pots. The inner pots are pure, and the outer pots are impure.

והתניא: אלו ואלו טמאות! אמר רבי חמא בר עוקבא: בשכלי אומנותו בידו, מפני שיד הכל ממשמשת בהן.

The Talmud asks: But isn’t it taught in a baraita: Both these inner pots and those outer pots are ritually impure? R' Ḥama bar Ukva said: That baraita is referring to a case where the tools of the potter’s trade are in his hand, indicating that he intends to sell his pots. Since all potential buyers touch pots when examining them before purchase, the concern is that among those people there is one who is ritually impure.

והתניא: אלו ואלו טהורות! אמר רבי חמא בר עוקבא: בשאין כלי אומנותו בידו.

The Talmud asks: But isn’t it taught in another baraita: Both these inner pots and those outer pots are ritually pure? R' Ḥama bar Ukva said: That baraita is referring to a case where the tools of the potter’s trade are not in his hand, indicating that he does not intend to sell his pots. Therefore, strangers will not touch them at all.