In what sense does he die without Musar?
Sanhedrin 106b: This teaches about Do'eg. Before he died, he forgot his learning 1 .
Rashi: He dies because he did not take Musar.
Malbim: After [getting used to sinning], he does not accept Musar, which is what Hashem's punishments can scare him. Even if Hashem punishes him, he will not take Musar. He will cling to his folly.
Lev Eliyahu (Shemos p.156): How can we learn forgetting Torah from lacking Musar? They are the same, for Musar is Torah.
What is "Ivalto"?
Malbim: It is casting doubt on everything. He does not believe in punishment via Hashgachah - he says, perhaps it is chance. He does not take Musar, for he attributes everything to chance!
