Comentário sobre Tahorot 10:6

וניתזה צנורא (and spittle splashed forth) – spittle splashed forth from the mouth of a commoner who is speaking, and the spittle that exits from the mouth of a commoner defiles people and vessels according to the Rabbis, and all the more so food and liquids.

One who was standing and speaking by the edge of the cistern and some spittle squirted from his mouth, and there arises the doubt whether it reached the cistern or not, the condition of doubt is regarded as clean. If the spit went into the vat and reached the wine, the wine would be impure. However, the Tosefta explains that the Mishnah rules that the wine is pure because the spit may have been absorbed into the walls of the vat and it may not have reached the wine. Therefore, the vat is pure.

פסיקו טהור – for we said that the edge of a cistern collected the ejection of spittle and prevents it from descending into the wine. And our Mishnah is speaking about a plastered cistern that does not receive ritual defilement. But in the Tosefta [Tractate Taharot, Chapter 11, Halakha 12] they stated that the cistern of [olive] oil is ritually impure, because the oil smoothens the edge of the cistern and [the ejection of spittle] smoothens and descends below to the oil that is in the cistern.