As we have learned throughout Masechet Menahot, a standard meal-offering is made up of solet – fine wheat-flour – mixed with oil and frankincense that is prepared in one of a number of different ways. There are meal-offerings that are made differently – e.g., the minhat ha-omer, brought on the second day of Passover that is made from barley or the minhat sotah, brought by a woman who was suspected of an extra-marital affair, which does not include oil and frankincense – but those are not voluntary meal-offerings.
What if someone decided to bring a meal-offering, but specifically stated that he wanted to bring it in a manner that was unusual?
The Mishnah on today’s daf (=page) deals with that question. According to the Tanna Kamma (=first), whatever statement was made must be corrected so that a proper meal-offering will be brought. Thus, if someone says “I accept upon myself a meal-offering of barley” he must bring a minhah of wheat. If he said “I accept upon myself a meal-offering from ordinary flour” he must bring a minhah made of solet. If he said that he would bring a meal-offering that did not include oil and frankincense, the minhah that he brings must include them. If he said that he would bring it with solet measuring half an isaron, he must bring a full isaron, which is the normal amount of flour that is brought.
Rabbi Shimon disagrees with the Tanna Kamma and rules that in all of these cases, since the type of offering that he committed to bring cannot be brought, the individual does not have to bring a meal-offering at all.
The first approach of the Gemara is to identify the Tanna Kamma of this Mishnah with Bet Shammai, who says that when someone speaks we always listen to the first statement that he makes. Since, in this case, the first thing that the person said was that he wanted to bring a meal-offering, that is what he must do, even if his later qualification makes that impossible. Ultimately, however, Rabbi Yohanan explains that the Tanna Kamma of our Mishnah would agree that if the person bringing the offering insisted that he only wanted to bring a minhah made of barley (or one of the other unusual cases), he would not be able to do so and would be free of any obligation. If his response was that he simply was unaware of the proper way meal-offerings were brought, and he really intended to commit to bring an ordinary meal-offering, then his first statement obligates him in a korban minhah.