Mishnayos Taharos Perek 8 Mishnah 7

אחורי כלים שנטמאו במשקין – that [the Mishnah] took/used the term, "אחורי כלים"/the outer sides of utensils, is because they were lenient, for a vessel whose outer part was ritually defiled with ritually impure liquids, its outer sides are ritually impure, but its inside – its handles, its rims/borders and its hands are ritually pure because the ritually impurity of liquids to defile vessels is from the Rabbis, they were lenient concerning it. But if its inside was defiled by impure liquids, all of it is defiled.

מטמאים את המשקין – even that which is non-consecrated [liquids].

ואין פוסלין את התרומה – and even that of heave-offering.

ר' יהושע אומר מטמאין את המשקין ופוסלין את האוכלים – Rabbi Yehoshua derives (in Tractate Niddah 7b) that the outer sides of utensils defile foods of heave-offering through an a fortiori/Kal VaHomer from the law of a person who immersed himself that day/טבול יום. Just as a person who immersed himself that day does not defile liquids and the Sages did not decree on a person who immersed himself that day that he defiles the liquids, nevertheless, he defiles the foods of heave-offering, as it is written (Leviticus 22:7): “As soon as the sun sets, he shall be pure; and afterward he may eat of the sacred donations, [for they are his food],” for he is not ritually pure to eat heave-offering until his sun has set, for the Biblical verse is speaking about heave-offering/Terumah. The outer sides of vessels that defile the liquids, does it not follow that they would invalidate the heave-offering? But Rabbi Eliezer did not concern himself with this a fortiori/Kal VaHomer, because the outer sides of utensils that are defiled by liquids is according to the Rabbis, and the person who immersed himself that day/טבול יום is from the Torah, and that which is Rabbinic, we don’t make an a fortiori [argument] on something from the Torah.

שמעון אחי עזריה – because Azariah dealt with practical maters and he would supply food to his brother Shimon who engaged in Torah study, therefore he is called by the name of Azariah, his brother.

לא כך ולא כך – we do not defile unconsecrated liquids nor do we invalidate/make unit food of heave-offering, but we do defile liquid have-offering, and those liquids of heave-offering, we defile at first degree of ritual impurity with foods of heave-offering that became second-degree of ritual impurity, and those foods invalidate/make unit other foods of heave-offering. And this is that we state that foods of heave-offering to liquids of heave-offering, “things that defile you do not defile me,” meaning to say, “the outer sides of a vessel that defiled you do not defile me, for they do not invalidate foods of heave offering, bur you defile me.” But the Halakha is according to Rabbi Eliezer.