The Maggid from Mezritch said: “The matter of Mattan Torah [The Giving of the Torah] is to draw the Ten Commandments within the Ten Utterances with which G-d created the World.” In other words, our spiritual goal on the holy days of Shavuot is to combine the matters of the physical world with the teachings of the Torah so that they mesh and become one.
This would answer a difficulty in the Talmud. The Gemara in Pesachim 68b relates a dispute as to our behavior on the holidays. Should one devote the entire day to spiritual pursuits or should one divide his or her activities between spiritual and physical enjoyment? The Gemara then states that even the one who holds that on the other holy days one should be totally immersed in the spiritual, requires physical pleasures — eating and drinking — on Shavuot. One would think it should be the opposite: The other days — those that celebrate our physical freedom from slavery (Pesach) and our physical protection from the elements in the desert for 40 years (Sukkot) — should involve physical pursuits, but the holy day of The Giving of the Torah should be totally of the spirit! If one realizes that our job is to combine the spiritual world of Torah with the physical world, one realizes why one is required to enjoy both types of pleasure on Shavuot.
This would explain the reason one must not interrupt between the donning of the tefillin of the arm and the tefillin of the head. [Ashkenazic custom is to say a separate blessing on each; Sephardim do not interrupt even with a blessing]. The tefillin of the arm symbolize the mundane activities and actions of the physical world while the tefillin of the head represent the spiritual pursuits. Since we must not separate the two, we are forbidden to interrupt between donning the two types of tefillin.
In Shulchan Aruch, siman 47:10, we are instructed to recite blessings before embarking on the study of Torah every morning. Although we interrupt our learning at different times during the day, the blessing said in the morning is sufficient for all learning that day. Why is this so? We see with other commandments that are repeated throughout a day with interruptions — like sitting and eating in a sukkah — that we do, in fact, recite a blessing each time we do the mitzvah, not merely once in the morning for the whole day.
An interruption takes us away from the performance of the commandment and, therefore, we are required to say a new blessing when we perform the mitzvah again. One must keep Torah on one’s mind all day long. There are laws that outline how one is to dress, speak, do business, relate to others, etc. The laws of the Torah involve every aspect of life. So long as one is awake, one does not really take one’s mind off the Torah. Even while involved in mundane pursuits, the involvement is constant. Therefore, one set of blessings per day is sufficient.
The day the Torah was given is also a day annually that one may draw on potent spiritual emanations that fill the atmosphere on that day. The ability to re-accept devotion and submission of all of one’s pursuits, material as well as spiritual, to the dictates of the Torah is available every year on Shavuot. This day, more than the other holy occasions during the year, is a day to resolve to mesh the physical aspects of our lives with the lofty ideals and principles of our Holy Torah.
May our renewed dedication find favor in the eyes of Hashem so that He will bring the coming of Moshiach and complete redemption speedily and in our days.