When did David sing this Shirah?
Rashi: It was in his old age, after all his afflictions passed and he was saved from all of them. 1
Malbim citing Mahari: He composed it in his youth, when he was amidst his afflictions. Each time Hashem saved him, he sang it - "b'Yom Hitzil Hashem Oso." In David's old age, he gathered all his praises into a special Sefer (Tehilim), for one who isolates himself to say in front of Hashem for all particular things that one needs in his lifetime, he will find a Mizmor or Tefilah to pray. It has wondrous Segulos; it was written with Ru'ach ha'Kodesh. This Mizmor was repeated there, for one who was surrounded by many difficulties and was saved from them, like David, to pray it. Since "Tefilah l'Ani Chi Ya'atof" (Tehilim 102) is for one who isolates himself, he changed many things to apply to an individual's needs
How did David know that all his afflictions had passed? Adoniyahu's rebellion was close to David's death! Perhaps he sang this afterwards. (PF)
Why was Sha'ul singled out? He was among David's enemies!
Rashi (from Sifri Ekev 52): He was the biggest enemy and pursuer of David. This is like "Tish'ah Asar Ish va'Asah'el" (2:30), "Lechu Re'u Es ha'Aretz v'Es Yericho" (Yehoshua 2:1), "veha'Melech Ahav Nashim Nochriyos
This Shirah is also in Tehilim (Perek 18), with differences. Why is it also here?
Malbim: Refer to 21:1:1:2.
