Rashi (4, citing Targum Yonasan): Me'Chametz is [something obtained] via Ones (extortion), like "Ashru Chamutz" (Yeshayah 1:17), "mi'Kaf Me'avel v'Chometz" (Tehilim 71:4).

Rashi (4): [Priests of the Ba'al say,] the Torah forbids "Se'or Lo Saktiru" (Vayikra 2:11); idolatry permits Haktarah of Chametz in a Todah.

Radak (4): The Torah said "Al Chalos Lechem Chametz Yakriv Korbano" (Vayikra 7:13) ? they do so to idolatry. Even though [Kohanim] did not burn the Chametz, they did burn the Emunah from the Korban [Todah] that comes with Chametz. The idolaters burned the Chametz.

Malbim: They announced that they should burn Todah from Chametz, just like in Beis Hashem they offered Todah with loaves of Chametz.

Rashi: They sang, and said 'this Korban is pleasing [to the idolatry] and accepted.'

Rashi (4): [Priests of the Ba'al say,] the Torah said "Lo Se'acher Leshalmo" (Devarim 23:22); idolatry says to remind everyone who volunteered and forgot ? he will put to his heart and remember ¹ .

Radak: You do like a "Mikra Kodesh" to idolatry. You announce that the nation bring voluntary offerings on the day of the festival!

Malbim: Aside from obligatory Korbanos, they called Nedavos ? everyone should bring what his heart volunteers.

Malbim: They announced all these matters, "for so you, Bnei Yisrael, loved" serving the calves and their Korbanos.