Who is "Chacham Lev"?
Rashi: He learned Chachmah from his Rebbi.
R. Yonah: He uses his Sechel to find new matters of Chachmah; he understands a matter amidst another matter.
Malbim: Chacham is one who received the laws of Chachmah, but there is still war in his heart against images of desire and intentional sin. Chacham Lev is one whose heart (the power that rules) has the nature of images of Chachmah; he has no internal war. Amidst habit and learning, it became like nature for him.
Why is Chacham Lev called "Navon"?
Rashi: In the end he will be Navon via delving into his Chachmah.
Malbim: Navon understand a matter amidst another matter. He engages to understand the laws of Chachmah, until in the end they become like Da'as. He knows them as clearly as something sensed. He can easily conquer images of desire, since he understands the laws of Chachmah - "b'Lev Navon Tanu'ach Chachmah" (14:32). However, he has much work until he understands everything - "Lev Navon Yevakesh Da'as" (15:14). Since the images of Chachmah are like nature in him, he is called Navon. Even if he did not attain the reasons for Chachmah via Tevunah, he understands them via the nature of Chachmah itself; it does not contradict his Nefesh's nature.
How is "Mesek Sefasayim Yosif Lekach"?
Rashi: When one gives reasons for his words to a Talmid, and makes the matters sweet with Ta'amim (reasons, or taste), he increases learning.
R. Yonah: Just like a Navon is Mechadesh matters of Chachmah via investigation and thought, so he increases learning when he says Divrei Chachmah with his lips. His lips cannot contain matters that are mixed, flimsy or weak. He strengthens the claims and adds reasons to what he heard from all his teachers. Regarding Resha'im it says "Im Tamtik b'Fiv Ra" (Iyov 20:12). Their lips strengthen their intents.
Malbim: A Navon brings Chachmah to the level of Da'as. The lips hints to Da'as, like I explained "b'Sifsei Navon Timatzei Chachmah" (refer to 10:13:1:3). Also a Chacham Lev who reached the level of Navon due to his nature and habit, "Mesek Sefasayim Yosif Lekach" if he puts Chachmah on his lips like something known with Da'as, which is fluent on his lips, which are external. "Yosif Lekach" is to teach that take new teachings into the Kelali of Chachmah - "Yishma Chacham v'Yosif Lekach" (1:5). He does not understand via the ways of Binah, rather, via habit of Chachmah, which is received, therefore it uses an expression of Lekach, which is receiving.
