Sheviis, Chapter 7, Mishnah 7. In the previous Mishnah we learned that a rose is considered fit for human consumption, and therefore the laws of the sanctity of Sheviis apply to it. Our Mishnah works with that same assumption, and deals with the law of a mixture of a Sheviis rose in oil.
A new rose in old oil:
A "new" rose means a rose of Sheviis, at a time when we are still in the Shemittah year itself - it is therefore new, since this is the year in which it grew. If one soaked it for a long period in "old" oil, that is, oil from the sixth year, it is enough that he remove the rose from the oil, and the oil is permitted. The oil is not affected by the Sheviis rose that was placed into it, because as long as we are still in the seventh year the time of biur has not yet arrived, and therefore everything is permitted.
An old rose in new oil:
But if the rose is "old," that is, a Sheviis rose from the year that has passed, and we are already in the eighth year, then the time of biur has arrived. In a case where one places an old Sheviis rose into new oil of the eighth year, the question arises whether the rose, which is already subject to the laws of biur, affects the new oil. The Mishnah's answer is "chayavim b'viur" - they are obligated in biur: although these are two different species - the rose on the one hand and the oil on the other - and ordinarily a substance mixed with a different species is not significant, here, since the rose imparted taste into the oil, the oil becomes forbidden and is obligated in biur.
Carobs and wine:
According to the explanation we are following, the next two cases deal with a situation after the time of biur has arrived: new carobs, which are subject to the laws of Shemittah, "shekevashan b'yayin yashan" - that he pickled in old wine, or "yeshanan b'chadash" - old carobs that he pickled in new wine. In both cases, since the time of biur has passed, "chayavim b'viur" - they are obligated in biur.
"Zeh haklal":
From here the Mishnah formulates the principle: "kol shehu b'nosen taam, chayav l'vaer min she'eino mino" - whatever imparts taste, one must remove a substance mixed with a different species. There are two possibilities before us:
A different species: two different species, such as the wine and the carobs, or the rose and the oil. The Sheviis prohibition affects the permitted substance mixed with it, whether before Sheviis or after it, and once the time of biur has arrived one must remove it - provided that it imparted taste.
The same species: literally the identical species. The halachah is that the prohibition applies "b'chol shehu," in any amount at all, and even in a minute quantity one must remove and destroy it.
The Mishnah concludes: "sheviis oseres kol shehu b'mino, veshelo b'mino b'nosen taam" - Sheviis produce prohibits in any amount when mixed with its own species, and when mixed with a different species, when it imparts taste. Just as this rule was established regarding other matters, so it applies to Sheviis as well: when mixed with its own species, Sheviis prohibits even in any amount at all, even in the most minute quantity; and when mixed with a different species, where the two species are different, it prohibits only when it imparts taste - when the taste can be detected.
It is worth noting that there are additional ways to learn this Mishnah, some of them easier to understand and some more difficult. We have explained it according to the Bartenura.