What is the significance of not returning to Egypt?
Rashi: I promised "Lo Sosifun Lir'osam Od" (Shemos 14:13). It did not help - against their will, Ashur is their king. Their sin caused them to be slaves to Ashur, for they refused to repent.
Radak: They should not have returned to Egypt to request help, for I told them "Lo Sosifun Lashuv ba'Derech ha'Zeh Od" (Devarim 17:16). Had they repented to Me, they would not have needed help from Egypt!
Malbim: Hashem wanted to lighten their yoke. Even though due to their sins they were forced to be subservient under Melech Ashur, had they not rebelled to send messengers to Soa Melech Egypt (due to this Melech Ashur was angry at them and exiled them) Melech Ashur would not have made a heavy yoke against them. Our verse teaches, I warned and counseled them not to return to Egypt to send messengers to [their king], since Ashur was their king. Since they refused to repent, it was decreed that Ashur be their king. It was improper to annul their Bris and return to Egypt to rebel against Melech Ashur.
What do we learn from "v'Ashur Hu Malko"?
Refer to 11:5:1:1, 3.
Radak: Bal Korcho (against his will), Ashur is his king. He will serve him and send a gift to him every year. Had they repented to Me, kings of the nations would not have ruled over them, like in the days of David and Shlomo, when they did My will, and so I promised them - "u'Mashalta b'Goyim Rabim u'Vecha Lo Yimsholu" (Devarim 15:6).
