דבר אל-כל-עדת בני-ישראל ואמרת אלהם קדשים תהיו כי קדוש אני יקוק אלקיכם: איש אמו ואביו תיראו ואת-שבתתי תשמרו אני יקוק אלקיכם: אל-תפנו אל-האלילם וגו’ וכי תזבחו זבח שלמים ליקוק וגו’
Speak to the entire congregation of the Children of Israel and say to them: “You shall be Holy, for I am Holy; I am Hashem your G-d. You shall revere your mother and father, and you shall observe My Shabbos; I am Hashem your G-d. Do not turn towards the false gods…When you offer a peace offering to Hashem…
Parshas Kedoshim is chockfull of mitzvos, both interpersonal and between man and G-d. Sometimes it is hard to discern why the mitzvos are presented they way they are, but if one were to investigate thoroughly, sometimes their labor will be fruitful. One such example is at the very beginning of the parsha. We are told to be Holy, for Hashem is Holy. Then we are told to revere our parents, and observe Shabbos. Then we are warned against idolatry, which is followed by the concept of bringing a voluntary peace offering to Hashem. What can we glean from the juxtaposition of these mitzvos?
What does it mean to be Holy? Our Sages teach us that we are to sanctify ourselves with that which is permitted to us. Holiness in this context refers to פרישות, abstinence from permitted things. Someone who goes beyond the letter of the law of the Torah and refuses pleasures or activities even though they are permitted is called Holy. Such a person could easily justify giving in to their desires, as they are in fact permitted. Someone who can work on themselves to even overcome permitted desires is on a very high level. If this is an injunction that we are to work on, why is up to us? If it is proper to refrain from something that is permitted, why didn’t the Torah explicitly forbid it?
How do most people fulfill the majority of the mitzvos that appear in the Torah? Very often it’s behavior that was engrained in them from their childhood. If the child was behaving against the Torah, their father would reprove them and direct them in the proper direction. As such, it’s not apparent in the person’s fulfillment of these mitzvos a desire to fulfill Hashem’s will. Nor is it apparent that they are serving Hashem out of love. This is something they’ve always done, so why wouldn’t they continue to do so? The only way to demonstrate our sincere to desire to connect with Hashem is through voluntary service. This is accomplished with פרישות. Doing more than what is necessary.
These ideas are portrayed by the verses we started with. A person should revere their mother and father, and therefore observe Shabbos. Meaning, one’s parents instill in them the concept of Shabbos, and teach them how to properly observe it. Similarly, the parents teach not to worship idols. This prohibition is a prototype for all the severe prohibitions in the Torah. How then will their service of Hashem be recognizable? What shows that the person is sincerely interested, and not just following the way they were raised? One way is bringing a voluntary peace offering. This kind of a mitzvah is analogous for those things which a person volunteers to take on, beyond the letter of the law. This makes them Holy, as they sanctified themselves through what was permitted to them. Good Shabbos
 Based on Chasam Sofer’s Toras Moshe I to Leviticus 19:2 [#2] (second half, starting with ואמר איש אמו ואביו; in the new Toras Moshe HaShalem they split this into its own paragraph)
 Leviticus 19:2-5
 Yevamos 20a; See also Rashi to v. 2
 See Mesillas Yesharim Chapter 13, who has his own approach to this question