The Shulchan Aruch (OC 494) cites the Rama who tells us that it is a custom to eat dairy on the first day of Shavuos. Contrary to popular belief however, one does not stop with eating a dairy meal. One should first eat a dairy meal and then afterward eat a meat meal. There are many reasons given for this custom. The one mentioned by the Rama is the following: Just as a roasted shank bone and roasted egg (Shtei Tavshilim) on the seder plate symbolize the Korban Pesach and the Korban Chagiga on Pesach, so too does eating a dairy meal with two breads and then a meat meal with two breads symbolize the Shtei HaLechem (Vayikra 33: 15-22).The Shtei HaLechem were two loaves of bread specially baked and brought in the Beis HaMikdash together with the Korban of an Olah and a Chatas. They were ‘waved’ together with them and then the two breads were eaten by the Kohanim.
By eating a dairy meal with two breads on the table, which represents the Mizbeach, and then again with a meat meal with two breads on the table, we symbolize the offering of the Shtei HaLechem.
In his Sefer Moadim U’Zmanim(V.8 - 79:319), Rav Moshe Sternbuch brings a novel reason for this Minhag. He says it is based on the Gemarah in Bechoros(6B) that discusses whether milk taken from a cow was considered Eiver Min HaChai (eating the limb of a live animal) before Matan Torah. If that is so then it is at MatanTorah that we are informed that milk is no longer considered Eiver Min HaChai and is Mutar. Rav Sternbuch says we eat dairy meal on Shavuos to symbolize that.
But Rav Sternbuch’s reason is difficult. The fact is the we see from an earlier incident in the Torah that milk was permitted.
Avraham Avinu gave cheese and milk to his guests and did not worry about feeding them something which is forbidden to them. If dairy products were forbidden by virtue of Eiver Min HaChai he would have been guilty of Lifnei Iver Lo Setein Michshol, the forbidden act of putting stumbling blocks in front of others. Lifnei Iver applies to Jews putting stumbling blocks in front of non Jews equally as it does to non Jews. We see that milk was not considered Eiver Min HaChai or Avraham wouldn’t have served it.
But one can find in the Meshech Chachama a scenario that can be used as a defense of Rav Sternbuch’s reason. It is possible that milk served by Avraham was from a Ben Pakua. A Ben Pakua is a surviving fetus within an animal that was properly slaughtered. Such an animal is considered Kosher without Shechita. And as such, taking milk from the ‘Shechted fetus’ would not be considered Ever Min HaChai under these circumstances. And therefore, pre Matan Torah under normal circumstances milk was considered Eiver Min HaChai.
Rav Sternbuch is still difficult, however. If one looks at the Talmudic source of Rabbi Sternbuch’s reason, one will see an expounding of the words “land of milk and honey” (Shemos 3). If it were true that milk was considered Assur before Matan Torah because of Eiver Min HaChai, it would never have used it as an element in extolling the virtues of Eretz Yisroel. And this Pasuk in the Torah is written before Matan Torah during God’s encounter with Moshe Rabbenu at the burning bush. Since milk was used in this way, it shows that milk must have been permitted well before the revelation at Sinai, thus refuting Rav Sternbuch’s explanation.
Taken from Torah L’Daas.
