“The nation prepared to receive the Torah, united together with one purpose” Talmud.
The underlying fundamental principles of the Torah were given in the 10 Commandments. Every one of the 613 Mitzvot can be found within the Decalogue.
Even though the Torah was given to the entire nation, and G-d spoke to all of the people together, the text of the Commandments was given in the singular form , and not in the plural.
Thereby teaching that every individual and every person has a connection to the entire Torah. However, this is obviously impossible for there are some Commandments whose performance is restricted to Cohanim only while some commandments are only performed by women or men, so how can any single person fulfill the entire Torah?
Our sages explained that when a person, for example, puts on Tefilin on his arm and head, it is not just the arm and head that have the Mitzva, but the whole person. Similarly, when people are united, they are as one, and the commandment performed by one person is shared by those with whom one is united.
Unfortunately divisive and fragmentation amongst the Jewish people, not only weakens our nation, but deprives a person of participating in the merit of those commandments which he or she is unable to perform. And that is why the prerequisite for the receiving of the Torah was the unity of the people.