What do we learn from "Ki Sanei Shalach"?
Rashi, from Gitin 90b #1: One who hates his wife should divorce her 1 and marry another.
Gitin 90b #2: One who divorces his wife is hated. This refers to Zivug Rishon. The Mizbe'ach cries over one who divorces his first wife - "Kesus Dim'ah Es Mizbach Hashem... Bagadta Bah v'Hi Chavertecha v'Eshes Brisecha" (13-14).
90b: This refers to Zivug Sheni. (The Gemara did not mention marrying another.) Radak - divorce her so she can marry another man, who will love her.
What is the meaning of "v'Chisah Chamas Es Levusho"?
Rashi: This is improper, to spread your Talis over her and establish her like your wife, when you have hatred of her and constantly vex and pain her.
Radak: He shows that he loves her and clings to her like his garment, which clings to his flesh, and he does not remove it. So he does not want to divorce her, and he hates her. This is a great betrayal. This is the Chamas that covers his garment!
Malbim: Even though also this (divorcing your wife due to hatred) is Chamas, it is hidden and covered Chamas. To keep her in his house and hate her is very blatant Chamas.
What do we learn from "v'Nishmartem b'Ruchachem v'Lo Sivgodu"?
Malbim: [Guard your Ru'ach,] and you will not need to come to hatred or divorce.
