A Torah observant Jew is often referred to as a shomer Torah u'mitzovs. The requirement to be shomer mitzvos is repeated several times throughout the Torah. What is the significance of being shomer - literally guarding - the mitzvos and why does this define the essence of a Torah way of life?
We are taught in Parshas Bamidbar about the mitzvah of shmiras Hamikdash, i.e. the guarding the Mishkan and later the Beis Hamikdash that was performed by the Kohanim and Leviim. According to many meforshim in Maseches Tamid, this "guarding" was not to actually protect the Beis Hamikdash, but rather was to indicate the significance of what we are "watching over." Similarly, shmiras hamitzvos is not merely performing mitzvos, but rather a declaration of the supreme importance of mitzvos in our lives.
What does shmiras hamitzvos entail above and beyond the fulfillment of mitzvos? Chazal articulate several times the dual obligation of "lishmor v'laasos - to watch over and to perform" the mitzvos, wherein lishmor refers to learning, and laasos addresses actual fulfillment. Learning Torah is the ultimate expression of shmira. If one truly views the mitzvos as the will of Hashem, one will spend all his time and effort to understand them. As such, the constant dedication to talmud Torah is the greatest acknowledgement of the significance of the mitzvos and thus the ultimate expression of shmiras hamitzvos.
Chazal relate that when one who learns Torah enters the next world, he is greeted with the words, "ashrei sheba l'kan v'talmudo b'yado - happy is the one who comes here with learning in his hand." This seems to be a strange way to describe one who learns; what is meant by the one whose learning is "in his hand"? The most precious of one's assets are not left for someone else to watch, but rather kept in one's own possession. Rashi comments that when Yaakov sent multiple gifts to Esav he also sent him previous jewels. Although not mentioned explicitly in the Torah, these jewels are alluded to by the pasuk that describes gifts sent from "the hand of" Yaakov, since what was in Yaakov 's own hand must have been the most important. Perhaps this is the "learning in one's hand" that Chazal are referring to. It is not mere learning that warrants the special welcome in the world to come, but rather it is the acknowledgement of the significance of Torah and mitzvos that is demonstrated by a lifetime of talmud Torah that accompanies a person to the next world and merits such a welcome.
As we approach the yom tov of Shavous we rededicate ourselves to shmiras haTorah v'hamitzvos. It is though the vehicle of talmud Torah that we demonstrate the significance of Torah in our lives. May we merit on this Shavous not only to receive the Torah, but also to hold it in our hands as befits the precious gift Hashem has bestowed upon us.