Seforno: It is referring to 15:31, warning Yisrael against indulging in Tum'ah - incorporating dealing with the spirit of Tum'ah and the demons. ¹

Sifra: Because we would otherwise have thought that, since they are not Chayav for bringing Korbanos on the Mizbe'ach, they are not Chayav for Shechutei Chutz either.

Zevachim, 116b: It implies that Nochrim are precluded from the Chiyuv of Shechutei Chutz. ¹

Sifra: To incorporate Geirim and Avadim in the Chiyuv of Shechutei Chutz.

Sifra: To teach us that Moshe taught the people word for word what Hashem told him - and this is a Binyan ha'Av that applies to the entire Torah. ¹

Nedarim, 78a: To teach us, via a Gezeirah Shavah "Zeh ha'Davar" "Zeh ha'Davar" from Parshas Nedarim, that, like Nedarim, Hekdesh is subject to She'eilah (by three Hedyotos or one Mumcheh). ²

Oznayim la'Torah #1 (citing the Midrash Rabah): It refers to the command not to sacrifice on Bamos that Hashem had already them when the Mishkan was erected and which they transgressed. ³ And the Torah is now in order not to create a Chillul Hashem.

Oznayim la'Torah #2: Whenever the word "ha'Davar" appears in the Torah, it teaches us the importance of speech. In the current Pasuk, it is referring to the declaration of Hekdesh - both vis-a-vis a Korban and vis-a-vis the Azarah - inasmuch as someone who Shechts or sacrifices a Korban (which he declared Hekdesh) outside the Azarah (which Yisrael sanctified) is Chayav Kareis. ⁴

Oznayim la'Torah #3: The word "Zeh ha'Davar" hints that, when the Beis-Hamikdash is not standing, one fulfils the Mitzvah of Korbanos with words - by learning about them. ⁵

Ramban, Moshav Zekenim: The Kohanim may not offer outside the Mikdash, and Yisrael must bring their Korbanos to the Kohanim, and not offer them by themselves.