What are the implications of "Kadosh Yihyeh Lach"?
Why does the Pasuk repeat the Inyan of Kedushah so many times in the current Parshah (See Pasuk 6, 7, 8 & 15)?
Rashi (19:2): Because Kedushah denotes abstaining from Arayos 1 - and wherever there is a Geder Ervah, there is Kedushah.
Targum Yonasan: The Torah mentions Kedushah twice in this Pasuk
To whom is Hashem saying "Ki Ani Hashem Mekadishchem"?
Ramban #1, Moshav Zekenim #1: He is saying it to the Kohanim. 1
Ramban #2, Moshav Zekenim #2: He is saying also to Yisrael. Since the Kohen offers "the bread of Hashem," through which He is Mekadesh everybody, you should consider the Kohen Kadosh.
Ramban: As the Parshah begins "Emor el ha'Kohanim".
QUESTIONS ON RASHI
Rashi writes that we are Mekadesh him Bal Korcho (against his will), and force him to divorce a Pasul wife. What is the Chidush? We always forcibly stop people from doing Aveiros!
Moshav Zekenim: One might have thought that this is only for what applies to all Yisrael, but a Kohen may opt to keep only Mitzvos of Yisrael, and not serve. Our verse teaches that this is not so.
Rashi writes that "Kadosh Yihyeh Lach" teaches that we conduct with him with Kedushah. Horiyos 13b learns this from "v'Kidashto"!
Mizrachi: Rashi explains according to the simple meaning. V'Kidashto teaches that we are Mekadesh him Bal Korcho, and Kadosh Yihyeh Lach is extra to teach that we honor him. Toras Kohanim supports this; it learns from v'Kidashto that we are Mekadesh him Bal Korcho.
Gur Aryeh: If not for "Kadosh Yihyeh Lach", "v'Kidashto" would teach that we honor him . Now that Kadosh Yihyeh Lach teaches that we honor him, v'Kidashto teaches that we are Mekadesh him Bal Korcho.