How should your trust be in Hashem?
Rashi: I inform you to trust in Hashem and engage in Torah. Do not say 'how will I abandon my work? How will I be financed?'
R. Yonah: The intent of all the Musarim that I arranged for you, is to get to Bitachon. All good Midos must bring a person to fear - Taharah and Kedushah bring to Yir'as Chet. Bitachon is from the highest levels in Yir'as Chet.
Malbim: This refers to "Hat Aznecha u'Shma Divrei Chachamim" (17), that your trust should be in Hashem. I.e. you will hear the laws of Chachmah from Chachamim, who received them from Hashem, and trust in Hashem who knows their secret and truth, and you will have no doubt about them.
Why does it say "Hodaticha ha'Yom] Af Atah"?
R. Yonah: Just like these Musarim helped me to reach Bitachon, so I hope that they will help you.
Malbim: After [you hear Chukei ha'Chachmah, and trust in Hashem and have no doubt about them], "v'Libecha Tashis l'Daiti" (ibid.) - I informed you the reasons of Chachmah and explained them with proofs of Da'as, so also you will know. Aside from trusting in Hashem, who knows their reasons and secrets, you will know what you can understand of them.
