What is the purpose of this Mizmor?
Rashi: David prayed it for his son Shlomo. He saw with Ru'ach ha'Kodesh that Shlomo will ask Hashem for a heart to hear (understand) Mishpat.
(Rashi 16, citing Chazal): This Mizmor discusses Melech ha'Mashi'ach. Radak #2 - and so he is called "Shlomo" in Shir ha'Shirim (8:12) - "ha'Elef Lecha Shlomo."
Rashi (20), Radak #1, Malbim: David said it in his old age, when he made Shlomo king; it says at the end "Kalu Sefilos David ben Yishai." Radak - it was at the end of his life, when he was lying on his bed. This Mizmor concluded his Tefilos and songs. This concludes the second of the five books of Tehilim. Those who arranged them 1 did not make it the last, for it is proper to close the Sefer with words of praise and Mizmorim of Hallelukah, and those Mizmorim are for the future, when Yisrael will return from Galus.
Brachos 9b: David composed 103 Mizmorim, but did not conclude Hallelukah until (Mizmor 104, in which) he saw the downfall of Resha'im. (This implies that he wrote Tehilim in the order we have them! -PF)
Why does it say "Mishpatecha l'Melech Ten"?
Rashi: [Give to him] the Chachmah of Your laws that You commanded in the Torah.
Radak: Give to him Da'as and understanding, so he will not err in Mishpat, rather, he will judge correctly; verse 2 explains this verse.
Radak citing Shocher Tov: Just like You judge without witnesses and warning, so Shlomo my son will judge without witnesses and warning 1 . Hashem agreed - "va'Yeshev Shlomo Al Kisei Hashem" (Divrei ha'Yamim I, 29:23). Can a human sit on His throne?! It is of fire (Daniel 7:9)! Rather, he judged like his Creator, without witnesses and warning, like the case of the two Zonos (arguing about whose baby died).
Malbim: The primary Mishpat is straightness; it is the foundation via which lawmakers gauge all particular rules. Philosophers agreed that it is of Hashem; man cannot attain it. David asked that Hashem give this to the king, and all particular laws will follow from it. This is like Shlomo himself requested "Havin Lishmo'a Mishpat" (Melachim I, 3:11). I.e. the foundation of Mishpat should be planted in his heart, just like they are in the Supreme lawmaker. Mishpat is Bein Adam l'Chavero; also refer to 72:1:4:3.
We can say also according to the opinion (refer to 72:1:1:3) that the Mizmor discusses Mashi'ach. Sanhedrin 93b learns from "va'Haricho b'Yir'as Hashem" (Yeshayah 11:3) that he will be able to judge via smell; the Sanhedrin killed Bar Kochba because he could not do so (so he was a Navi Sheker for claiming to be Mashi'ach - Yad Ramah). (PF)
To whom does "l'Melech" refer?
Rashi #1: It and "l'Ven Melech" both refer to Shlomo.
Rashi #2 (from Shocher Tov): It refers to David; all the Mishpatim, i.e. afflictions, should be finished on me, and do Tzedakah for my son, that he will have Shalom in his days.
What is "Tzidkasecha"?
Rashi: It is justifying the verdict.
Radak: It is Your straightness; You judge straightly.
Malbim: Tzedakah 1 is correctness of deeds Bein Adam la'Makom. Also this one can know only via Hashem, so he requested also this.
I.e. Tzedek. Here he does not refer to Tzedakah to Aniyim! (PF)
Why does it say "l'Ven Melech"?
Radak: You commanded kingship to his father and to him; therefore make him a virtuous king.
Radak (20): Notzerim say that this "Shlomo" is their savior; he was Ben Melech, and saved "Bnei Evyon" (verse 4), i.e. those who descend to Gehinom. "Yered k'Matar" (verse 6) refers to Divinity descending from Shamayim. One can easily refute them. If "Shlomo" is Divine, the verse mentions four Divinities (Shlomo, Elokim, Melech, Ben Melech), and they say that there are three! Why did the son ask his Father for His Mishpat and Tzedakah? It says "Yis'u Harim Shalom la'Am" (verse 3). There was no Shalom in their savior's lifetime! "Yira'ucha Im Shemesh" (verse 5, all will fear Hashem) - there were many sinners after him! "He will rule from sea to sea" (verse 8) - the body did not rule over anything, and the Divine rules without limit! His enemies (Yisrael) did not lick his earth, and kings did not give to him gifts or bow to him, and all (i.e. Yisrael and Yishmaelim) do not serve him (verses 9-11). "Vi'Chi" (verse 15) was not fulfilled on his body, and there is no need to pray for the Divine!
Malbim: Setting up a king and establishing his throne is initially via Mishpat - "u'Shfatanu Malkenu" (Shmuel I, 8:20), but it will last for generations after him only in the merit of Tzedakah - "vi'Tzdakah Yikon Kisei" (Mishlei 16:12). Therefore, he requested Mishpat for the king, and Tzedakah for the Ben Melech (the continuity of the kingship).
