Rashi: Sechel is a source of life for one who has it.

R. Yonah: It is proper to investigate and understand via Sechel the ways that are pleasing to Hashem.

Malbim: This explains how a Chacham Lev understands the laws of Chachmah, until they become like Da'as. It is a source of life from which a Chacham Lev draws Da'as. Sechel is the owner of the source. Even though Binah does not understand the laws of Chachmah, they are understood via Sechel - a sharp power in man to understand the truth of hidden matters, also the laws of Chachmah and spiritual matters above man's Binah. There is also Sechel Tov, i.e. Ru'ach ha'Kodesh that takes effect on a Chacham Lev - "Toras Chacham Mekor Chayim

Rashi: Afflictions of Evilim come to them via Iveles. The verse means that Iveles is afflictions for Evilim.

R. Yonah #1: The nature of Sechel is to recognize good and evil, and recognize the ways pleasing [to Hashem]. However, a person can pervert his natural Sechel and falsify his straightness via habituation to coveting and choosing evil. Since he desires the act of Aveiros, and he chooses the love or company of Resha'im, his heart is reversed. His Sechel turns into a destroyer.

R. Yonah #2: Desire blinds the eyes of Sechel and falsifies recognition, like "Ki ha'Shochad Ye'aver Pikchim vi'Ysalef Divrei Tzadikim" (Shemos 23:8). A person does not see his own guilt, nor guilt of his beloved (Kesuvos 105b). Therefore, Musar Evilim (when they rebuke their colleagues, to show to them the proper path) is Iveles. It teaches them to do evil - to be haughty and go in the ways of their hearts, to oppress, covet and switch a world that endures for a fleeting world. Evilim closed the eyes of their Binah and blocked the source of their natural Sechel via desires, to the point that their Sechel teaches them that evil is good - "Chadal Bni Lishmo'a Musar Lishgos me'Imrei Da'as" (19:27). Also Resha'im support the Musar of Evilim - "v'Atah Anachnu Me'asherim Zedim Gam Nivnu Osei Rish'ah Gam Bachanu Elokim va'Yimaletu" (Mal'achi 3:15). It is called Musar based on Evilim's mindset, just like idolatry is called Tifletzes and Musar based on its worshippers - "Musar Havalim Etz Hu", "Tiflatztecha Hisi Osach" (Yirmeyah 10:8, 49:16).

Malbim: Even though Evilim disgrace Chachmah and Musar, for they cast philosophical doubts on the laws of Chachmah and the roots of Musar, which are built on Yir'as Hashem, Sechel clarifies their truth via Musar Haskel. It afflicts the Evvil and clarifies their folly and doubts via Sechel.. This is in the power of a Chacham Lev - "v'Da'as l'Nafshshecha Yin'am", "Lehatzilcha mi'Derech Ra me'Ish Medaber Tahpuchos" (2:10, 12). "V'Eved Evvil l'Chacham Lev" (11:29) - via Chachmas Lev, he knows Musar Evilim and the refutation of their Iveles and doubts.