Why does it say "v'Atem"?
Radak: Until now discussed their children who will later leave Galus. This verse returns to rebuke that generation in Yerushalayim.
Malbim: This returns to discuss that generation, which serve idolatry and came to seek the Navi.
Why does He tell them to serve their idols?
Rashi: Do not show the nations that you are called on My name when you come to the Navi to ask Torah from him. When he tells you My words, you do not heed Me - "v'Hinecha Lahem k'Shir Agavim" (33:32) -they hear His words, and do not do them.
Radak #1: This is not a command, rather, a threat, like "Semach Bachur b'Yaldusecha" (Koheles 11:9) - rejoice, and see what will occur to you in your end!
Radak #2: It is better that you serve idolatry alone, and not bring to Me your gifts and serve idolatry - this is Chilul Hashem! Malbim - they serve idols and separate gifts to Hashem. They separate the Bechor for Hashem, and offer it to Molech - "uvi'Seis Matenoseichem b'Ha'avir Bneichem ba'Esh" (31). It would be less Chilul Hashem if you served only idolatry. Now, Goyim think that you serve Hashem; when He punishes them, the Goyim say "Am Hashem Eleh ume'Artzo Yatza'u" (36:20).
Why does it say "v'Achar Im [Einechem Shom'im Elai]"?
Radak: The Vov is [extra], like the Vov in "va'Yisa Avraham Es Einav" (Bereishis 22:4). Im is like Asher, like "Ad Im Dibarti Devarai" (Bereishis 24:33).
Radak citing Targum Yonasan: After you sinned, you did not want to accept My word.
What are "b'Matenoseichem uv'Giluleichem"?
Rashi: You separate firstborns with the name Bechorah, like I commanded, and after My name is called on it, you offer it to idolatry!
