When did David compose this Mizmor?
Rashi (2): It is about when David came to the circle where Sha'ul was sleeping. He took the spear and flask, went away, and called "ha'Lo Sa'aneh Avner" (Shmuel I, 26:14). I.e. now you must prove to Sha'ul that he chases me without reason. If I wanted, I would have killed him!
Malbim: It is based on Sha'ul's men, who enticed him to pursue David again. They said that [David did not pass up an opportunity to kill Sha'ul, rather,] he found the corner of his garment 1 . Also this is called "Al Tashches", like the previous Mizmor, and opposes liars and slanderers.
Rashi (Sanhedrin 49a): Avner said that it got torn on a thorn and fell off, and David was hiding there and found it.
Why does it say "l'David Michtam"?
Refer to 16:1:2:1-4 and the notes there.
