Dairy on Shavuos

(17) You shall bring from your settlements two loaves of bread as an elevation offering; each shall be made of two-tenths of a measure of choice flour, baked after leavening, as first fruits to the LORD.

(6) Regarding the two goats of Yom Hakippurim, the [absence of] one invalidates the other. Regarding the two lambs of Shavuot, the [absence of] one invalidates the other. Regarding the two loaves [that accompany the lambs], the [absence of] one invalidates the other. Regarding the two rows [of the showbread], the [absence of] one invalidates the other. Regarding the two dishes [of frankincense], the [absence of] one invalidates the other. Regarding the rows and the dishes, the [absence of] one invalidates the other. Regarding the two kinds [of cakes] used in the offering of the nazirite, the three kinds used for the red cow, the four kinds [of cakes] used in the thanksgiving offering, the four kinds [of species] used for the lulav, and the four kinds used for the [purification of the] leper, the [absence of] one invalidates the others. Regarding the seven sprinklings [of the blood] of the red cow, the [absence of] one invalidates the others. Regarding the seven sprinklings between the poles of the ark, and of those toward the curtain and upon the golden altar, the [absence of] one invalidates the others.

(4) One who ate cheese, and wants to eat meat, needs to remove from the table leftover bread that he ate with the cheese. And it is forbidden to each cheese on the tablecloth that they ate bread on. (And vice-versa is similarly forbidden.) (So is implied in the Aruch.) And all the more so is it forbidden to cut cheese, even cold, with a knife that they usually use to cut meat. And not only that, but even the bread that they eat with the cheese is forbidden to cut with a knife that they use to cut meat. And vice-versa is also similarly forbidden. However, via stabbing into hard ground, it is permitted. (Beit Yosef, quoting A"Ch and Kol Bo). But, all of Israel already is accustomed to having two knives and to mark one of them, so it is distinguished, they are accustomed to marking the dairy one, and it's not right to change a custom of Israel.

(3) It is prohibited to fast immediately after the holiday of Shavuot. Ramah: And we do not say Tachanun from the beginning of Rosh Chodesh Sivan until the 8th day, which is after the post-holiday day (Hagahot Maimoni, Hil' Tefillah Umnagim). We have the custom to spread out plants on Shavuot in the synagogue and in houses, as a memory for the happiness of the receiving of the Torah. We have a custom everywhere to eat dairy food on the first day of Shavuot. And it seems to me that the reason is: It is like the two foods that are taken on the evening of Pesach, a reminder of the Korban Pesach and a reminder of the Korban Chagiga, so too we eat a dairy food followed by a meat food, and we bring with them two loaves on the table in place of the Mizbeach, and thus there will be a reminder of the two loaves that were brought on "The day of the Bikkurim."

(14) ...Like the two that we cook... What this means to say is that on Passover we make a remembrance of the Koraban passover (on our seder plate with the bone) thus we do on Shavout by remember the "Shtei Halechem" that was brought, and therefore we eat a dairy meal and afterwards we eat a meat meal and we need to bring with the meal 2 different breads because it is forbidden to eat Milk and Meat from the same bread and this serves as our remembrance (having 2 breads we force ourselves to have by having a dairy meal then followed by a meat meal) "Shtei ha lechem

(6) There are many reasons for eating dairy, I will copy the reason written in the Zohar: the previous seven weeks were in parrallel to the seven clean days a woman counts before immersing in the mikvah, we know that blood becomes milk, this is parallel to the movement from judgement to mercy, and the practice of our fathers is in our hands to fulfill. However, it is important to be careful not to violate any prohibitions (see Yoreh Deah 89)...

(12) Dairy foods - See Magen Avraham and I also heard in the name of a Gadol who said a correct reason for this: that when Bnei Yisrael stood at Har Sinai and accepted the Torah(When the 10 commandments were revealed, and through this all the parts of the Torah were also revealed to them, like that Rav Sadya Gaon writes, that the 10 commandments sustain the whole torah) and they went down from the mountain to their homes they found nothing to eat immediately except for dairy foods because for meat they would need much preparation to slaughter with a checked knife like Hashem commanded... And to clean out the strings of forbidden fats and blood, and to rinse and salt(the meat). Also to cook in new vessels because their previous vessels had been used to cook meat (that they now discovered was actually trief) had been used in the last 24 hrs (which is what is forbidden Biblically) so their old vessels were forbidden to them, therefore they choose on account of the time to eat dairy foods and we do this as a commemoration of this.