English Basic Explanation - Chapter 7
The opening verse of Chapter 7 informs us that David composed this Psalm in response to an incident involving a person named "Kush the Binyaminite." Nowhere in Tanach do we find a person with this name, and the Sages thus concludes that David refers here to King Shaul, who was from the tribe of Binyamin and pursued David until his (Shaul's) untimely death at the hands of Philistines. David introduces this Psalm with the word "Shigayon," which many Rabbis understood as a derivative of the verb "Sh.G.H.," which refers to a mistake or misjudgment. It is thus commonly understood that David speaks here of a wrong he committed against King Shaul. Rashi brings three possibilities in identifying the particular incident to which David refers in this chapter:
1) According to one view, David speaks here of the song of praise he sung to the Almighty after Shaul's death (Shemuel II, chapter 22). The Gemara (Mo'ed Katan 16b) writes that the Almighty reacted angrily to David's song of triumph celebrating Shaul's downfall, and it is to this "Shigayon" that David refers in this Psalm.
2) Rashi advances a different approach, claiming that David composed this Psalm when he came under attack by the mighty Philistine warrior Yishbi (Shemuel II 21:16). The Talmud (Sanhedrin 95a) writes that God held David responsible for the many tragedies that occurred as a result of his strained relationship with Shaul, and punished David by allowing Yishbi to mount an attack against him. According to Rashi, it was during this difficult hour in David's reign that he composed and offered this prayer.
3) Finally, Rashi cites a view held by several commentators that David refers here to the incident when he severed the corner of Shaul's garment (Shemuel I 24:5). During his pursuit of David, Shaul unknowingly entered the cave where David and his men hid, affording David the opportunity to kill his pursuer. Instead, David cut the corner of Shaul's garment which he later (24:12) showed to Shaul as proof of his loyalty, as he had the opportunity to kill him but refrained from doing so. Despite David's noble intentions, severing the corner of Shaul's royal garb constituted an infringement on the honor due to the King of Israel, for which he was punished. According to this view, David here appeals to the Almighty to forgive him for this crime, emphasizing that he severed Shaul's cloak not out of malice and disrespect, but rather as a means of saving himself from Shaul (verses 4-6; see Rashi).
According to all these approaches, David petitions God to save him from his enemies who threaten him, begging that He ignore their prayers (verse 8) and judge him favorably on account of his innocence and upright conduct (verse 9). While acknowledging that he has committed a "Shigayon," a misjudgment of sorts, David insists that his crime pales in comparison with the cruelty and heartlessness shown to him by his enemies. He proceeds to elaborate on the theme of divine justice, the anger and fury with which the Almighty responds to evil, and the ultimate downfall of evil's perpetrators. Despite his own shortcomings, David expresses his confidence that God will judge him favorably and condemn his vicious adversaries to defeat.