Shabbat 112B

דלמילתיה מנא הוא, אבל הכא ⁠— למילתיה לאו מנא הוא.

it is fit as a utensil for its usual purpose, i.e., it can be used as footwear. However, here it is not fit as a utensil for its usual purpose.

ומי אמר רבי יוחנן הכי? והאמר רבי יוחנן: הלכה כסתם משנה, ותנן: סנדל שנפסקה אחת מאזניו ותיקנה ⁠— טמא מדרס, נפסקה שניה ותיקנה ⁠— טהור מלטמא מדרס, אבל טמא מגע מדרס. מאי לאו לא שנא פנימית ולא שנא חיצונה!

The Talmud asks: Did R' Yoḥanan in fact say that the halakha is in accordance with R' Yehuda, who says that if the outer strap broke the sandal becomes pure? Didn’t R' Yoḥanan say: The halakha is in accordance with an unattributed Mishnah? And we learned in a Mishnah: A sandal that became ritually impure with impurity imparted by the treading of a zav, and one of its ears broke and he repaired it, this sandal is still impure with ritual impurity imparted by treading, since a broken ear does not render the sandal useless and it remains a utensil. If the second ear broke and he repaired it, it is ritually pure in the sense that it no longer renders other objects ritually impure in the same way a vessel that became a primary source of ritual impurity by means of impurity imparted by treading does, since when both ears tear it is no longer a utensil. However, it is itself ritually impure with ritual impurity imparted by treading due to contact with a vessel that is impure, i.e., contact with itself. Since the sandal now has only one torn ear, it is still considered a utensil which is capable of contracting impurity, and it is as if it contracted impurity from itself in its previous state. Is this statement not an indication that there is no difference whether it was the inner strap or the outer strap that broke, as no single ear that breaks terminates the sandal’s use? This contradicts R' Yoḥanan’s statement.