Why is there a Yud at the end of "Melashni"?
Radak: This is extra, like the Yud in "ha'Magbihi Lasheves" (Tehilim 113:5). The word is a four-letter root; Meloshan has the same grammatical form as Meshofet.
Why did he say "Atzmis"?
Radak: I rebuke him and cut him off from in front of me; he will not see my face any more. This is the opposite of other kings 1 , who draw close slanderers, in order to monetarily punish those whom they slander. I hated the slanderer, and I did not punish anyone without witnesses. I cut off the slanderer, for I established him to be a liar. Even if he says Emes, he sins via testifying alone. One of three whom Hashem hates is one who sees another sin, and testifies alone about him.
Mesilas Yesharim (Perek 11): Anything that can cause damage or shame to another, whether in front of him or not in front of him, this is Leshon ha'Ra, which Hashem hates and abhors. One who speaks Leshon ha'Ra, it is as if he denies a fundamental of Emunah (Erchin 15b).
Malbim: Most people accept Leshon ha'Ra. I do not - I punish only the one who spoke!
What is the significance of "Gevah Einayim u'Rchav Levav"?
Radak: This is like it says "Rom Einayim u'Rchav Lev" (Mishlei 21:4). His eyes are elevated to look at lusts of the world, and he widens a place in his heart and thinks about them. After his eyes and heart are on them, he pursues them - "v'Lo Sasuru Acharei Levavchem v'Acharei Eineichem" (Bamidbar 15:39). The eyes and heart are two merchants of sin (Yerushalmi Brachos 1:5).
Malbim: He has the bad Midos of haughtiness and lust.
What do we learn from "[u'Rchav Levav] Oso Lo Uchal"?
Sotah 5a #1: Hashem says 'I cannot dwell in the world with a haughty person'. We read Oso (him) like Ito (with him).
Sotah 5a #2: Hashem says 'I cannot dwell in the world with those who speak badly of others' (mentioned earlier in this verse).
Rashi: I cannot bear that such a person be my friend, lest I learn from his ways.
Radak: I cannot see such a person, or I cannot bear him.
Malbim: I cannot bear him at all.
