Mishnayos Taharos Perek 4 Mishnah 5

על ספק בית הפרס - heave offering/priest’s due that entered into an area in which uncertainty exists concerning the location of a grave or a corpse, that this is a field in which a grave was plowed up and it is doubtful if there within a bone a barley-corn’s bulk from the corpse.

ועל ספק עפר הבא מארץ העמים – that dust that comes from the lands of the nations, we have doubts regarding the mass of earth from a grave containing parts of a decayed human body. And it is taught concerning the land of the nations/ארץ העמים and the area in which uncertainty exists concerning the location of a grave or a corpse/בית הפרס, they (i.e., the Rabbis) decreed that they would defile through contact and through lifting.

ועל ספיקן של בגדי עם הארץ – for regarding all of them we are in doubt if his menstruating wife sat upon them.

ועל ספק כלים הנמצאים – for we don’t know if they are ritually impure.

ועל ספק רוקין – for perhaps they are of a person with gonorrhea or a woman with flux, or that of a menstruating woman or someone who just gave birth.

מי רגלי אדם שהן כנגד מי רגלי בהמה – it teaches us a noteworthy point, and we don’t say that since these (i.e. urine) are from beasts, those also are from beasts, and even though there are two doubts (i.e., a compound uncertainty) for a leniency, the doubt regarding beasts [and] the doubt regarding a human being, and even if you can assume that [both] are from a human being, perhaps, the person is pure. And Maimonides explains through reference to the Tosefta (see Tractate Makhshirin, Chapter 3, Halakha 13 and Tractate Taharot, Chapter 5, Halakha 2), as for example, that the urine of a ritually impure man was mixed with the urine of a beast in equal measure, and this is nearby the urine of cattle, and we have a doubt if the appearance of the human urine was nullified and that all of them are ritually pure, or that they weren’t nullified and all of them are ritually impure.

על ודאי מגען שהוא ספק טומאתן (because of certainly touching them which is a manner of doubt in respect to their [imparting] uncleanness)- he knows with certainty that priest’s due/heave offering came in contact with them, but he doesn’t know if they are ritually impure or not, as we have explained the doubt in all of them.

וחכמים אומרים ברשות היחיד תולין – on the doubt of their contact, and we don’t burn them because it is a compound uncertainty which is ruled as a leniency, there is a doubt whether it touched and there is a doubt whether it did not touch, and even if you can assume that it came in contact, there is doubt of whether they are ritually impure or ritually pure. But the Halakha is not according to Rabbi Yossi who stated that on doubt of their contact we burn them [in the private domain].