Where does Rashi say that less than a kezayis of oil does not become impure?

Question

Wikiyeshiva has an article in Hebrew on the question of the Beis Yosef as to why Chanukah is 8 rather than 7 days (after all they had oil for one day).

The article quotes an answer on the approach that they only used a small amount of oil for each day and that oil lasted miraculously the whole night – even the first night. It says:

יש שכתבו שלא הייתה להם עצה אלא לשים חצי כזית שמן ותו לא, וזאת היות והמנורה הייתה טמאה בטומאת מת[7], ומתכת הטמאה בטומאת מת מטמאה כמת (חרב הרי היא כחלל – שבת קא: ועוד), וא"כ כל שמן שישימו במנורה יטמא. ואין פתרון אלא לשים חצי כזית שמן, שלשיטת רש"י (דרוש מקור) אינו מטמא (ברכת יצחק - מובא בספר דיני חנוכה, הוצאת דגל ההלכה, ירושלים תש"ס, עמ' קנ).

That they had to use half a kezayis of oil and no more because the metal menorah was impure with the impurity of a dead body and therefore any oil put in the menorah would become impure too. If they used half a kezayis of oil, according to the opinion of Rashi, the oil would not become impure. The article is from the Bircas Yitzchok in the book “Laws of Chanukah” brought out by “Degel HaHalocho”, Jerusalem 5760, page 150. No source is given for the “opinion of Rashi”.

Where does Rashi say that less than a kezayis of oil does not become impure?

Answer 1

Where does Rashi say that less than a kezayis of oil does not become impure?

--> Possibly nowhere, this is against the opinion of Rashi (min Hatora), and against all opinions (miderabanan⁽²⁾) see bellow:

The Tosfot in Nazir 36a, paragraph "amar Rabba" ⁽¹⁾ said that according to Rashi, a food can become unclean min Hatora, even if he is less than a Kezayis. Tosfot said that for this reason Rashi did not accept one Girsa in the suggia of Mikpa.

There is a Mishna in Tevul Yom 2, 3 that said:

If part of a stew of hullin containing garlic and oil of terumah is touched by a [defiled person who] had bathed that day, only that part that was touched becomes unfit [to be eaten].

The Talmud Bavli (Nazir 36a and Pesachim 44a) asks about this Mishna:

Now, in discussing this it was asked why the part touched should become unfit. {Tosfot said that the old Girsa of the Gemara, "in all books" contains an addition: "it (the touched part) is not KeBeytsa (the touched teruma's garlic and spice has not a volume of one egg.)"}. This Gisra is right according to Rabenu Tam, who stated that Min Hatora, a food cannot became unclean if its volume is less than the volume of one egg. But Rashi refuted this Girsa, because he was thinking that a food can become unclean Min Hatora regardless of its volume. Rashi gave a proof from the Torat Kohanim which learn from a verse that food becomes unclean regardless of its volume. Rabbenu Tam, said that this is not a true drasha but an Asmachta. According to Rabbenu Tam, food becomes unclean when its volume is less than Kebetsa, but rabbinically only. Thus Rabbenu Tam rehabilitated the old version of the Gemara. Gemara asked why the touched part became unclean (the word is PASAL פסל which has a Toraic connotation according to Tosfot).

Summary, according to everybody less than kezayit of oil can be unclean, according to Rashi Min Hatora, according to Rabenu Tam Miderababan.

The wikipedia annotation wrotes "דרוש מקור" (needs sources) meanwhile, on top of that, we are very surprised.

_{BTW, the controversy between Rabenu Tam and Rashi gives a proof that the Perush Rashi is not from Rashi, as The Shem Hagedolim reported in name of Yad Mal'achi, because this perush ruled as Rabenu Tam about food less than Kabetsa. This perush is according to the Shass Vilna from Rabbi Yehuda Bar Natan.}

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⁽¹⁾

ובעיני רש''י לא ישרה זאת הגירסא שבכמה מקומות פי' שאוכל מקבל טומאה אפי' בכל שהוא כדדרשי' בת''כ אוכל יטמא מלמד שמטמא בכל שהוא יכול אף לאחרים בכל שהוא ת''ל אשר יאכל אוכל הנאכל בבת אחת והיינו כביצה ור''ת אומר דאסמכתא בעלמא הוא דבמס' אהלות (פי''ג מ''ה) תנן פחות מכביצה אוכלין וקתני סיפא זה הכלל הטמא אינו ממעט והא דדייק והא [לא] הוי כביצה צ''ל דלאו אשמן דייק דמשקין מטמאין בפחות מרביעית אלא אשום פריך וא''ת ומאי פריך והרי שום ושמן אחת הוא שאין מקבלין טומאה פחות מכביצה מדאורייתא מ''מ פסלי שפיר ואע''ג דאין מקבלין טומאה מדאורייתא מ''מ מדרבנן מטמאי ומאי פריך הא דפסיל ר''ל מדרבנן וי''ל דלישנא דפסל משמע מדאורייתא:‏

⁽²⁾ May be that in Mikdash some rules derabanan are skiped regarding tahara but it is very improbable.

In Masechet Pesachim, 16a, there is an opinion following which "beverages" have no uncleanness at all Min Hatora (Yosef Ben Yoezer, according to the tradition of Rav). This point is still not clear for me. The Rambam and the Raavad in the first chapter of Tum'at ochlim ruled that oil may be unclean min Hatora.