What are "Oyvai Sheker"?
Rashi: They hate me due to Sheker. They testify about me [evil deeds] that never crossed my mind.
Radak: They hate me for no reason 1 , like "Son'ai Chinam." Also "Ach la'Sheker Shamarti" (Shmuel I, 25:21) is 'for naught.'
Malbim: Usually the hatred is for a reason, e.g. [the one he hates] harmed him. Here it was Sheker, for David did not do evil to them.
Is there a difference between "Oyvai" and "Son'ai"?
Malbim: The Oyev's hatred is revealed. He is openly happy [at my downfall]; therefore, it says "Al Yismechu Li." The Sonei's hatred is in his heart. He does not reveal it, just he winks - "Yikretzu Ayin." Usually the hatred is due to a blemish or problem in the one he hates - they are Son'ai Chinam.
What is "Yikretzu Ayin"?
Radak: They wink to mock and scorn. The same applies to the lips - "Koretz Sefasav" (Mishlei 16:30).
