When the Torah tells us about the giving of the Torah it begins, "In the third month from when the Children of Israel came out of Egypt, they came to the Sinai desert." And the Talmud tells us about the giving of the Torah, "Three lights (Torah, Nevi'im and Kesuvim), to a triple nation (Kohen, Levi and Yisrael), in the third month."
Why specifically the third month? Isn't the purpose of Torah to draw down that Hashem is one? In Torah unity is the most important thing, one not three. Why specifically three?
When all alone and there is nothing to challenge the unity, you don't know if it is true unity, if it will stand up to the test of time. The only way you could know if it is true unity is if it has been challenged.
When the unity is challenged by a negative force, there are two ways of upholding the unity, you can totally ignore or negate the opposition to the unity, or you can harness the negative force, until it itself becomes a positive force upholding the unity.
As far as true unity is concerned, the second way, in which the challenging force becomes a uniting factor is far superior, because it becomes part of the unity, and it shows that the unity is a true one.
This will help us understand why specifically the third month. The first three months are Nissan, Iyar and Sivan.
In Nissan there was the exodus from Egypt, full of miracles, it was so overwhelming that there was only Hashem, perfect unity, but there was nothing to challenge the unity.
Then came the month of Iyar, which was the challenge, because in the month of Iyar the whole month they counted sefira, which is working on the body and animal soul to become in sync with the neshama, and with Hashem. The body and animal soul are selfish by nature, they only want what will give them pleasure, they aren't interested in Hashem and the Torah, but we can train and harness them until they become a uniting factor.
Sivan is the month we received the Torah, Hashem came down on Mount Sinai, there was the fusion of the physical world and G-dliness, we got the ability to permeate the physical world with G-dliness. So the third month, Sivan, is the essence of unity, true unity.
As Tanya teaches us that the difference between Torah and Mitzvos.
When you do a mitzvah, you become a chariot to Hashem, just as a chariot has no will of its own and goes wherever its master wishes for it to go, so too, when you do a mitzvah, you have no will of your own, you are just doing Hashem's will.
Mitzvos are connected to the month of Iyar, because Mitzvos are done with the body and with the physical and all the days of the month are connected with Sefiras HaOmer, when we work on ourselves to become more of a chariot to Hashem.
And this perhaps is why Iyar is an acronym for Avraham, Yitzchak, Yaakov and Rachel, in Kabbalah they are the legs of the Divine Chariot.
However a chariot although it connects you with Hashem, it doesn't make you one with Him, you are only, so to speak, attached.
On the other hand, Torah is the wisdom and will of Hashem, and the wisdom and will of Hashem is actually Him. When you study a part of Torah and know it well in all its details, you totally envelope Hashem with your mind and at the same time you are in the Torah you have learned, because you are into the subject, you are surrounded by Hashem. In other words, you are truly one with Him, it is the only totally true unity, total fusion of above and below, G-dliness and the mundane.
Now we understand why the Torah was specifically given in the third month, and why Torah is connected to the number three, because then you experience the highest form of unity, Hashem is one in everyone and everything.
Each and every one of us should take the time to learn Torah as much as we can and even more. If we do, we will surely merit the coming of Moshiach, when "the whole world will be filled with the knowledge of Hashem, like the water covers the sea." Total fusion. May it happen soon.