What is the meaning of "Levav l'Yachad"?
'Rashi': Your hearts and mine will be like one heart.
What is the meaning of "l'Tzarai"?
Radak: For the sake of my afflicters (Sha'ul and his supporters).
Why did he say "b'Lo Chamas b'Chapai"?
'Rashi': Sha'ul seeks to trap me for no reason. I did not do anything to him!
What is the meaning of "v'Yochach"?
Malbim: He will clarify. This was a Tefilah 1 , that if they came to help him, Hashem should put in David' heart love for them, and if not, he will [feel a need to] beware of them.
If this was a Tefilah, why did he say so to them? Indeed, "va'Yomer Lahem" could mean about them (like "va'Amar Pharaoh li'Vnei Yisrael" ? Shemos 14:3). However, "Basem" proves that he spoke to them! Rather, he told them that this is his Tefilah to Hashem. (PF)


