What is the meaning of "Al Tat Libi"?
Rashi: My heart should not lean to evil.
Radak: (After praying about what leaves his lips, he prays about his heart.) Just like now my heart is proper, so it should be always; evildoers should not be able to tilt it. If You will not help me to prepare my heart, it is as if You tilt it.
Malbim: The Yetzer should not entice his heart to an evil matter.
What is the meaning of "Lehis'olel Alilos b'Resha"?
Radak: To do an evil act.
Malbim: To do to evildoers according to their evil, i.e. not to kill Sha'ul and his men 1 .
Indeed, David had two opportunities to kill Sha'ul. When did he have an opportunity to kill Sha'ul's men? When they were sleeping, and he took Sha'ul's spear and flask (Shmuel I, 26:12). He could have killed a few of the 3,000 men, but then others would waken and kill him, for he is a Rodef! And why would he want to kill them, and not just Sha'ul? They would not kill him if he killed Sha'ul. Even if they held that Sha'ul's sons will inherit his kingship, Yehonason would be the next king, and they knew that he loved David! (PF)
What is "Es Ishim"?
Rashi: Im Anashim (with people).
What is the meaning of "u'Val Elcham b'Man'ameihem"?
Rashi: I should not recline [to eat] at their meals.
Radak: I will not desire to eat their delicacies. I.e. my heart will not be drawn to worldly lusts, like their hearts are drawn.
Malbim: I should not eat their delicacies, i.e. to go in their ways and counsel.
