Why does it say "veha'Banim"?
Rashi: Because it said "va'Avosam Pash'u" (3), it needs to clarify that their children are "Keshei Fanim."
What are "Keshei Fanim"?
Radak citing Targum Yonasan: They are brazen faced. This is like "Goy Az Panim" (Devarim 28:50). One who lacks shame, he is brazen and hard. Conversely, one who has shame, his face is soft, and it reddens when one rebukes him.
Orchos Tzadikim (Sha'ar ha'Azus): They persist in their evil.
Malbim: This is another shortcoming. If the Navi rebukes them from Sechel, they contradict him.
What are "Chizkei Lev"?
Malbim: If one warns them about Hashem's punishments, they do not fear.
Why does it say "Ko Amar Hashem"?
Radak: Tell to them this Nevu'ah in My name.
Malbim: Even though there are reasons why they will not accept your words, I send you to them. The primary Shelichus is to tell them that you are Hashem's Navi, so they will know that Hashem sends a Navi to them and oversees their matters. They should not say that they are like all the nations, that Hashem does not supervise them.
