What counsel should you hear?
R. Yonah: The previous verses warn the father to rebuke the son. Now it warns the son to hear counsel and accept Musar.
Malbim: If you want to inherit Chachmah, you must hear Etzah - "Shome'a l'Etzah Chacham" (12:15), and accept Musar. The Musar is due to fear of Hashem and His punishment.
How will you grow wise in your end?
R. Yonah: It will be via Musar, while you are a Na'ar. In one's youth, it is proper to think about his end, so he will repent in his end. He should not say 'I will wait until I mature, and then I will prepare my heart for Avodas Elokim.' One does not know when he will die, like the coming verse "Rabos Machashavos b'Lev Ish"; repent one day before your death (Avos 2:10). Does one know when he will die?! Rather, repent today; perhaps you will die tomorrow (Shabbos 153a). This way, all his days are in Teshuvah; "b'Chol Es Yihyu Vegadecha Levanim" (Koheles 9:8).
Malbim: The goal is to know Chachmah that will help to have happiness in the end.
