This is because the first commandment ‘Onochi Hashem’ includes all of the two hundred and forty-eight positive ‘Mitzvos’ and the second of the ‘Aseres Hadibros’ ‘Lo Yihiyeh Lecho’ includes all of the three hundred and sixty-five negative Mitzvos (Prohibitions). The prohibitions fall within the category of רָצוֹא – advancing and separating and distancing from the world. Positive Mitzvos (which are about connecting to Hashem) fall within the category of שוֹב – return by drawing G-dliness down into the world.
Explanation from Tanya and Other Sources
Onochi Hashem includes: As the Alter Rebbe brings in Tanya “The first two commandments: אנכי and לא יהיה לך,” comprise the entire Torah. For the commandment “אנכי ” contains all the two hundred and forty-eight positive precepts, while the commandment “ולא יהיה לך ” contains all the three hundred and sixty-five prohibitive commandments. That is why we heard only these two commandments, “I am...,” and “You shall not have...,” directly from Hashem, while the other eight commandments were transmitted by Moshe, as our Sages have said, for they are the sum total of the whole Torah. This also appears in the Shnei Luchos Habris at the Beginning of Parshas Yisro he writes: The commandments: " אנכי and לא יהיה לך" tell us that אנכי, is the source of all positive commandments, and לא יהיה לך tells us that the same G–d is the source of all prohibitive commandments. Similar things are mentioned in the Iben Ezra and in the Zohar.
The prohibitions: These two categories of Mitzvah are paralleled with רָצוֹא וָשוֹב. The prohibitions which are about distancing oneself from sin.
Category of רָצוֹא: Which is the want and strive to distance from materialism and from any involvement with the material world and to grow closer to Hashem. As are the prohibitions that distance one from certain elements of the material world.
Positive Mitzvos: Are Mitzvos which encourage one to get involved with material objects and be instrumental in elevating worldly things through a personal interaction with the materialism.
