For what do their sins join with their fathers' sins?
Rashi: I will pay you for both of them together.
Radak: They joined to lengthen your Galus.
Malbim: The fathers were punished only for their sin, for they sinned openly "on mountains and hills." The children are punished for their sins and their fathers', for they sinned [covertly] in gardens, graves and places of carcasses (4).
Why does it specify Haktarah?
Radak: That evil deed, they denied Me and served idolatry.
Malbim: Haktarah was on mountains, and blasphemy on hills.
Why does it say "Cherefuni"?
Radak: When they served idolatry on the hills, they blasphemed, disgraced and denied Me. I commanded not to serve idolatry, for one who does so denies Hashem.
What is the meaning of "u'Madosi Fe'ulasam Rishonah El Cheikam"?
Radak: First I will measure their actions to them themselves, and afterwards to their children.
Malbim: First I will punish this generation for their own sins - it was greater, for they feigned piety - and afterwards for their fathers'.