Avodah Zarah 68A

שאין ראויה לגר ⁠— אינה קרויה נבלה.

and any carcass that is unfit even for a ger toshav to consume, e.g., one that turned rancid and is unfit for consumption, is not called an unslaughtered carcass with regard to its prohibition.

ורבי מאיר, ההוא למעוטי סרוחה מעיקרא, ורבי שמעון ⁠— סרוחה מעיקרא לא צריכא מיעוטא, עפרא בעלמא הוא.

And what can R' Meir respond to this? He could say: That verse is written to exclude meat that was rancid at the outset, i.e., that was not fit for consumption even before the animal’s death, due to a defect in the animal. By contrast, a carcass that was fit for consumption when the animal died and was consequently rendered forbidden remains forbidden even when it becomes rancid. And R' Shimon could counter that meat that was rancid at the outset does not need specific exclusion by the verse, as it is considered as mere dust and does not fall under the category of an unslaughtered animal carcass.

אמר עולא: מחלוקת שהשביח ולבסוף פגם, אבל פגם מעיקרא ⁠— דברי הכל מותר.

§ Ulla says: This dispute between R' Meir and R' Shimon is with regard to a forbidden food that enhanced the flavor of a dish when it first fell into it and subsequently detracted from its flavor. In this case R' Meir deems the dish forbidden, since the forbidden food enhanced its flavor at the outset. But in a case of forbidden food that detracted from the flavor of the dish at the outset, everyone agrees that it is permitted.

איתיביה רב חגא לעולא: יין שנפל לתוך עדשים, וחומץ שנפל לתוך גריסין ⁠— אסור, ורבי שמעון מתיר. והא הכא דפגם מעיקרא הוא, ופליגי!

Rav Ḥagga raised an objection to the opinion of Ulla from a baraita: Forbidden wine that fell into lentils, or forbidden vinegar that fell into split beans, renders the food forbidden. And R' Shimon deems them permitted. But here it is a case where the forbidden food detracted from the flavor of the dish at the outset, and the tanna’im disagree.