Why does it mention Teshuvah here?
Radak: Until now it discussed a father and his son. Now it discusses the man himself, when he repents from his deeds. Just like his sins will not be mentioned after he repents, so a Tzadik who retracted from his virtue and did unjustly, all his virtue will not be remembered (24).
Radak (6): After saying that the son will not bear his father's sin, and vice-versa, it says that he will not bear even his own sins, if he repents from them. Malbim ? not only regarding two different bodies, rather, even the same body, if he repented, will not bear previous sins.
Why does it say that he will live and not die?
Radak: He will live in this world, and not die in the world to come. The same applies to "Yechi Reuven v'Al Yamos" (Devarim 33:6).
Radak (6): Reward is included in living, and punishment is included in dying. Even though reward and punishment is much more encompassing, also Brachos and curses in the Torah are abbreviated. "U'Shmartem Es Chukosai? Asher Ya'aseh Osam ha'Adam va'Chai Bahem" (Vayikra 18:5) mentions life in place of all Brachos. Even though Onkelos translated 'in the world to come], va'Chai implies in this world, just like all Brachos and curses that the Torah foretells. However, va'Chai hints to the world to come 1 . "Ha'Chayim veha'Maves Nasati Lefanecha ha'Brachah veha'Kelalah u'Vacharta ba'Chayim Lema'an Tichyeh" (Devarim 30:19). Ha'Brachah veha'Kelalah are singular, for they are the Klal; the verse calls them life and death. Life with success and good is life; with evil, it is death. It says about one who succeeds "Ko l'Chai" (Shmuel I, 25:6); one with Tzara'as is called Mes ? "Al Na Sehi ka'Mes" (Bamidbar 12:12). Also an Oni is considered dead.
Radak (6, citing Rav Sadya Gaon): Life and death here refer to the world to come 2 .
Malbim: His body will not die, and he will live life of the Nefesh.
Radak: Also elsewhere, the Torah hints to the world to come, but the simple meaning is this world. Hashem told Adam "b'Yom Achalcha Mimenu Mos Tamus" (Bereishis 2:17) ? death includes all curses decreed on man due to eating ? "Arurah ha'Adamah Ba'avurecha b'Itzavon Tochelenah?; Kotz v'Dardar Tatzmi'ach Lach?; b'Ze'as Apecha?" (ibid. 3:17-19).
Radak: Indeed, the primary reward and punishment is in the world to come. However, here the Navi answers those who say that a son bears his father's sin, when they see the children's great afflictions in that generation; the fathers are not around. They did not complain about the world to come, for they knew only what they saw. The answer must be like the question!
