MIDRASH TEHILLIM
1.....(7.1)
Shiggaion "impulsive speech" of David, which he sang to the LORD,
"Even in your thought, you shall not curse a king, nor in your bedrooms shall you curse a wealthy man, for the bird of the heaven shall carry the voice, and the winged creature will tell the matter." (Kohelet - Ecclesiastes 10:20)
Indeed, for such curses even walls have ears.
God asked David: "Why do you curse Mine annointed? Do you not call Saul enemy?"
David replied, Master of the universe, do not fetch up against me words spoken impulsevely, as though they had been spoken deliberately.
2.....(7.3)
Shiggaion of David...
Rabbi Aha, When a man requests God to rebuff the insult that offered to him, he would not be punished for such a request. Why, then, should David have spoken of his request as Shiggaion, impulsive speech?
Rabbi Hinena answered, Because David rejoiced in some at the fall of Soul, as is said, He sang unto the LORD, concerning the matter of the Cush the Benjaminite, though it is written: "When your enemy falls, do not rejoice, and when he stumbles, let your heart not exult" (Mishlei - Proverbs 24:17)
Therefore, God said to David, If Saul's fate, or if your fate had been his fate, how many Davids would i have caused to perish for his sake.