Shabbos, Chapter 2, Mishnah 2. This mishnah continues the discussion we began in the previous mishnah: which oils are fit and which are unfit for use in kindling the Shabbos lights.
"Ein madlikin b'shemen sereifah b'Yom Tov":
The mishnah opens with a matter already mentioned in the previous mishnah - shemen sereifah, which is oil of Terumah that became tamei and whose law is that it must be burned. It may not be burned on Yom Tov, and therefore one may not kindle with it on Yom Tov. This explains the reason for the halachah taught in the previous mishnah, that shemen sereifah may not be used for kindling the Shabbos lights.
And this is the reasoning behind that halachah according to both of the opinions stated regarding it:
According to one opinion, the previous mishnah was speaking specifically about an Erev Shabbos that falls on Yom Tov, since one does not burn kodashim that are tamei or invalid on Yom Tov.
According to the second opinion, the mishnah was speaking about every Erev Shabbos, on account of a decree made because of an Erev Shabbos that falls on Yom Tov.
Either way, our mishnah clarifies and explains what we learned earlier: the reason shemen sereifah cannot be used for kindling is that one may not kindle with it and may not consume it on Yom Tov.
The opinion of Rabbi Yishmael - "Ein madlikin b'itran":
Rabbi Yishmael says: "Ein madlikin b'itran" - one may not kindle with itran. Itran is a by-product of pitch, and it has a foul smell, so one may not kindle with it out of respect for Shabbos. The concern is that a person will leave his house because of the bad odor and will not want to sit near the lights.
The view of the Chachamim:
The Chachamim disagreed with him and "matirin b'chol hashemanim" - they permit all the oils, and these are they:
"B'shemen shumshemin" - sesame oil.
"B'shemen egozim" - nut oil.
"B'shemen tzenonos" - oil of radish seeds.
"B'shemen dagim" - fish oil.
"B'shemen paku'os" - a type of melon whose seeds produce oil.
"B'itran" - even though its smell is unpleasant, the Chachamim permit this as well.
"B'neft" - the substance known as naphtha.
The view of Rabbi Tarfon:
Rabbi Tarfon says: "Ein madlikin ela b'shemen zayis bilvad" - one may kindle only with olive oil, and not like the opinion of the Chachamim, who permitted the use of the other oils as well.
In summary: In this mishnah we learned that one may not kindle with shemen sereifah on Yom Tov, and this explains the reason for the prohibition taught in the previous mishnah; that according to Rabbi Yishmael one may not kindle with itran out of respect for Shabbos, because of its foul smell; that the Chachamim permit all the oils - sesame, nut, radish, fish, paku'os, itran and naphtha; while Rabbi Tarfon requires olive oil alone.