Mishnayos Taharos Perek 4 Mishnah 1

הזורק. ככר לבין המטפחות – there is no difference whether he threw a ritually pure loaf among ritually impure keys, or whether he threw impure keys among the [ritually pure] loaves, and it is not known if the loaf came in contact with/touched the ritually impure keys, the loaf is ritually pure, for the [anonymous] Tanna/teacher of this Mishnah holds that someone who throws is like one who lacks the awareness/knowledge to be interrogated.

ר' יהודה אומר ככשר לבין המפתחות טמא – for Rabbi Yehuda holds that a person who throws (whether impure keys or loaves) has awareness/knowledge to be interrogated, and his [status of] doubt makes him ritually impure. However, when he threw [a ritually impure key among the loaves], it (i.e., the loaf) is ritually pure, since the defilement does not come to rest in a place but rather passes over the ritually pure [loaf], its doubt is [presumed to be] ritually pure. But the Halakha is not according to Rabbi Yehuda. And the [ritually pure] loaf and the [ritually impure] keys that our Mishnah uses, the same law applies for all the rest of the things that are thrown, but because it is the practice of people to throw a loaf and keys one to the other, because of that, [the Mishnah] took this [example].