Not eating meat on Shavuot is an ancient custom. One Midrash says that during the declaration of the Ten Commandments all the cattle, sheep and goats stood by quietly; not making a sound. It is only right for us to honor them by not eating their descendants on Shavuot
However, the custom is not simply not to eat meat. We should make an effort to eat dairy foods on Shavuot. Many reasons are given for this custom. One of them is that when Israel received the Torah, they felt rejuvenated and reborn. Just as an infant is nourished through milk, we too, should eat dairy on Shavuot to symbolize the birth of the Jewish nation.
Also the Torah tells us, “And Moshe was on the mountain forty days and forty nights” (Exodus 24:18). “Milk in Hebrew is “Chalav”. The numerical value of Chalav is 40 (Chet = 8, Lamed = 30, Vet = 2). This alludes to the 40 days Moshe stayed on the mountain receiving the Torah.
Dairy foods are milk products, and milk comes from mothers. On Shavuot we need to remember that in addition to the formal written Torah of Mitzvot; there is the informal Torah of Kindness that is on a woman’s tongue. (Proverbs 31:26)
This Torah of female kindness, which can be called the Torah of Miriam the Prophetess (Exodus 15:20) nourishes us like mother’s milk. It is so basic to our moral personalities that we usually are unaware of the great influence it has upon our character.
Eating dairy foods on Shavuot reminds us that we should never turn away from the Torah of our mothers or the ethics of our fathers (Proverbs 1:8).
Another sign is that Mothers Day usually comes about a week or two before Shavuot and Fathers Day comes a week or two after Shavuot The influence of our mothers precedes that of our fathers; just as the Torah of Kindness precedes the Torah of Mitzvot. This is especially true for those Jewish communities that are blessed to have women Rabbis.
Confirmation, held on Shavuot or the Sunday before or after Shavuot, was the first Jewish ceremony in which females could participate equally with males. It is Jewish custom in Reform congregations to serve dairy at Confirmation receptions.
Finally, the Haftarah reading for Shavuot is the Book of Ruth—an account of the most famous female convert to Judaism. According to a Midrash the souls of all future converts to Judaism were also standing at Sinai when Israel received the Torah.
According to Sefer HaPliyah, a 14th century Kabbalistic text, most converts to Judaism are gilgulim- reincarnated Jewish souls from previous generations that were lost to the Jewish people, who are now returning home to their original people.
Thus on Shavuot we should honor all the non-Jews who have joined the Jewish people over the centuries. It is fitting that families celebrate these wonderful additions to our family and our people, by eating on Shavuot, something special like blintzes, in their honor.
Here is an autobiography of Aliza Hausman, a convert to Judaism, who I think is a good example of a gilgul Jewish soul:
At 12-years-old, when I told my Catholic mother that I wanted to be Jewish, she slapped me silly. That was when I found out my family was staunchly anti-Semitic, despite the Star of David I stole from my mother’s nightstand. (She also wore a cross, and I’m still not totally sure what it was doing there.)
As the daughter of immigrants, I had only just realized that there were other options outside the Catholicism practiced in my home. Even living in Washington Heights, around the corner from Yeshiva University, I assumed everyone was also Catholic and had little altars at home where their mothers made offerings to saints.
It took a visit from a Holocaust survivor, a trip to Yeshiva University’s museum, and one excursion to the local library’s religion section, and I was sold. After all, as a child in Sunday school, everyone had drawn Jesus when we were told to draw G-d, and I had only squiggled my yellow crayon around and said “G-d is light.” The nun was perturbed. But I cringed whenever I heard “in his name we pray,” or when I saw all the idols in church.
It wasn’t until after college, many non-observant Jewish boyfriends later, that I rediscovered Judaism. My best friend, a sworn atheist, had met a rabbi and gone Orthodox. Instead of freaking out, as many of his friends did, I asked him for books and websites, and when I told my family about my plans to become Jewish, my sisters said, “Well, great… didn’t you always want to be Jewish?”