On Shavuot it is customary to eat dairy products. Why?

The Mishna Brura 494:12 explains that at the time of Matan Torah, God’s revelation at Sinai (the first Shavuot) B’nai Yisrael accepted upon themselves all of the mitzvoth (commandments). Since there was no time to properly prepare kosher meat (there were no delis in the desert) the only other choice was to eat dairy products.

Today, we eat dairy on Shavuot to remember that B’nai Yisrael ate dairy on the first Shavuot.

How do we know that milk is kosher?

The Gemara in Berachot 6b explains that one way that we know that milk (from a kosher animal) is fit for consumption is because in Shmot 3:8 God says “I will descend to rescue My people from the hand of Egypt and to bring them up from the land to a spacious land, to a land flowing with milk and honey (eretz zavat chalav u’dvash)…” If milk is not permitted, would the verse praise Eretz Yisrael with something that is not fit for consumption?

Before B’nai Yisrael received the Torah they may not have ever tried milk. It was only at the time of Matan Torah that they found out that milk was permissible.

In Shir HaShirim 4:11 we read (liral translation) “Your lips, O my bride, drop as the honeycomb: honey and milk (dvash v’chalav) are under your tongue; and the scent of your garments is like the scent of Levanon.” (Rashi’s allegorical translation reads: The sweetness of Torah drops from your lips, like honey and milk the Torah lies under your tongue…)

Since the Torah is compared to milk, it makes sense to drink some on Shavuot, the day that we received the Torah!