Parsha Kedoshim begins with a very important message:
קדשים תהיו כי קדוש אני ה אלהיכם
You shall be holy, for I the Lord your God, am holy (19:2).
Rashi explains that this statement was made during an assembly convened to highlight the importance of the matter, as it says-
דבר אל כל עדת בני ישראל
Speak to the entire congregation of the children of Israel
The Parsha proceeds with a series of laws, both moral and religious, among them repetitions of the ten commandment in slightly different wording.
איש אמו ואביב תיראו
man shall fear his mother and his father(19:3).
And אל תפנו אל האללים
..Do not turn to the idols(19:4).
You shall not steal (19:11).
But perhaps the most important message in this Parsha is:
ואהבת לרעך כמוך אני ה
You shall love your fellow as yourself, I am G-d(19 :18).
Because when a person loves his fellow as he loves himself, he will never commit the forbidden moral laws against society. The Parsha ends with the same message as with which it began:
והיתם לי קדשים כי קרוש אני ה
You shall be holy to me, for I the Lord am holy(20 :26).
Therefore we learn that only if we follow the Mitzvot can we be holy.