Radak: He composed it when he was fleeing Sha'ul or Avshalom. The latter is correct; the coming Mizmor proves this, like we will explain (refer to 71:1:1:1).

Malbim: This and the coming Mizmor he prayed when fleeing Avshalom, in his old age. This Mizmor is [essentially] the ends of [the last five] verses of Mizmor 40, for the miracle done for him in his youth when he fled Sha'ul. Also refer to 71:1:1:2.

Rashi: It is an expression of Tefilah, like "va'Anachnu b'Shem Hashem Elokeinu Nazkir" (20:8).

Rashi citing Shocher Tov: This is a metaphor for a king who was angry at his flock, and destroyed the pen and removed the flock and the shepherd. Later he returned the flock and built the pen, and did not remember the shepherd. The shepherd said, the flock is returned and the open is built, and I am not remembered?! So above this (69:36-37), it says that Hashem will save Tziyon, and Ohavei Shmo will dwell there - the pen is built and the flock is entered. The shepherd (David) was not mentioned! Therefore, it says here "l'David Lehazkir;