Rashi: This woman that you see in the Eifah, it is the Midah of the evil way that Resha'im go in. Now they are in it to be stricken in the same Se'ah (measure) that they measured out.

Radak: The angel told the Navi that the Eifah is the evil that was in Yisrael - the 10 tribes, who made the calves and began Avodas ha'Ba'al. Rish'ah is a noun, or an adjective.

Malbim: The woman sitting in the Eifah is evil. It was revealed and depicted in the form of a woman. She sits in the Eifah to teach that evil itself will punish the Rasha. It will measure out to the evildoer punishment according to his evil.

Rashi: Until now she was sitting. Now he threw her, and knocked her in it. This hints to punishments.

Radak: Hashem cast her into the Eifah - He measured for her like her measure (punished Midah k'Neged Midah).

Malbim: Via punishing the Resha'im through the evil itself, Midah k'Neged Midah, people recognize Hashem's punishments, and will fear to do evil. Via this, evil will cease and punishments will stop.

Rashi: This is to submerse her ¹ , so they will not steal any more, and their voice will not be heard to plunder the poor.

Rashi (11) and Malbim, citing Sanhedrin 64a: Anshei Keneses ha'Gedolah fasted for three days and asked Hashem to hand the Yetzer ha'Ra over to them. A lion of fire came out from the Kodesh ha'Kodoshim; Zecharyah told them that it is the Yetzer ha'Ra. He told them to throw it in a lead pot ² and cover it with lead - "va'Yashlech Osah El Toch ha'Eifah... Oferes Al Piha."

Radak: This was to sink her in Galus for many days. "El Piha" is in the mouth (opening) of the Eifah.

Malbim: The Kikar of lead in the Eifah's mouth stifles the voice of evil in the Eifah. Evil will seal its mouth when it sees that there is an Overseer who rewards and punishes.