Zevachim 97B

עד שיבלע בבשרה.

This teaches that this halakha does not apply unless the other food absorbs something of the sin offering into its meat.

יכול נגע במקצת חתיכה יהא כולו פסול? תלמוד לומר: ״יגע״⁠ – הנוגע פסול. הא כיצד? חותך את מקום שבלע. ״בבשרה״⁠ – ולא בגידין, ולא בעצמות, ולא בקרנים, ולא בטלפים.

One might have thought that if the sin offering touched part of a piece of something that absorbed flavor from the sin offering, the entire piece should become disqualified. To counter this, the verse states: “Whatever should touch its flesh should be sacred” (Leviticus 6:20), to teach that only the section that touches the sin offering is disqualified. How so? What can be done with an item when a section of it is disqualified? One slices off the section of the piece that absorbed the disqualified matter. Additionally, the verse states: “Whatever should touch its flesh,” but an item is not disqualified if it touches the sin offering’s sinews, nor its bones, nor its horns, nor its hooves.

״יקדש״⁠ – להיות כמוה. הא כיצד? אם פסולה היא ⁠– תפסל, [ואם] כשרה היא ⁠– תאכל כחמור שבה.

§ The baraita continues to interpret the same verse. “Whatever should touch its flesh should be sacred,” teaches: Whatever touches it becomes like it, with regard to its status. How so? If the sin offering is disqualified, due to any disqualification, whatever touches it becomes disqualified. And if it is fit, whatever touches it must be eaten in accordance with the stringent regulations that apply to the sin offering. Therefore, a piece of meat that touches the meat of a sin offering may be eaten only in accordance with the terms of the consumption of a sin offering, e.g., it may be eaten only by male priests, and only for one day and one night.