What is the structure of this Mizmor?
Radak: There are eight verses for each letter of the Aleph Beis. Each verse has one of the following words - Derech, Torah 1 , Edus, Pekudim, Mitzvah, Amirah, Dibur, Mishpat, Tzedek, Chukim or Emunah. They are the portions of the entire Torah. Each verse mentions one or more of them, but it refers to all of them.
Malbim: For each letter, there is a verse with each of the six matters listed in Mizmor 19 - Torah, Edus, Pekudim, Mitzvos, Chukim (this is in place of Yir'ah) and Mishpatim, and two of Devarecha, Imrasecha or Derachim.
Radak: Torah is the nature of the Mitzvos, how they are done, e.g. Toras ha'Chatas, Toras ha'Asham. The same applies to other Mitzvos.
Why are there eight verses for each letter of the Aleph Beis?
Radak: This entire Mizmor is about Mitzvos, Mishpatim, Chukim
Radak: Granted, some matters are seven, due to the seven Galgalim, seven Kochvei Leket (the sun, moon and five closest planets, and seven days of the week, based on the creation; 10 is the sum calculation.
Here, 'Midos' are ways of adding knowledge. Chushim are ways of transmitting knowledge. Interestingly, they are done with the five limbs special for sense, even though some are not connected to senses, e.g. speaking and writing. (PF)
Radak: It is clear how four senses pertain to Chachmah - one reads Seforim, hears teachers, says what he learned from and teaches others, and writes Seforim. The nostrils are close to the two front chambers of the brain, which have the power of illustration. The sixth way to acquire Chachmah is via those who tell. (Why this is not included in hearing Chachmah? - PF) If all say that a certain city exists, one knows that it does, even if he never saw it. Or, if researchers tell what they discovered. The seventh is sight of the intellect; it is the strongest.
This Mizmor is about Torah. Why does it include verses said when David was afflicted or fleeing?
Radak: The affliction distracted him from engaging in Torah and Chachmah.
Who are "Temimei Derech"?
Radak #1: They go in Toras Hashem, i.e. they learn. His path will not be complete if he does not learn - a Boor (ignoramus) cannot fear sin (Avos 2:6).
Radak #2: It is as if Derech is repeated - Temimei Derech go b'Derech Toras Hashem, for Derech Toras Hashem is the complete and pure path.
Radak #3: We re-arrange the words - those who go in Toras Hashem, i.e. learn, they are happy when they are Temimei Derech, i.e. they act purely from their learning, and go beyond the letter of the law.
Malbim: Tom Derech means that there is no blemish or lack in his way. His good path is fixed; he never veers from it. All his actions are l'Shem Hashem, and not for other motives or personal benefit. This is possible only if he goes in Toras Hashem - his path is based on Torah, and all his acts are because so Hashem commanded in His Torah 1 .
Malbim: This is unlike paths that philosophers made based on their investigations. They do oppositely if it will benefit them, for his path is not based on good, rather, what is useful, and human intellect.
What is "Torah"?
Radak: Torah is the nature of the Mitzvos, how they are done, e.g. Toras ha'Chatas, Toras ha'Asham. The same applies to other Mitzvos.
