Why does it say "Ani"?
Rav Sadya Gaon, Rashi: I guard the king's word.
Ibn Ezra: I command you
What is "Pi Melech"?
Rav Sadya Gaon: It is Mishmeres of his word [what he commanded to guard].
Rashi #1: It is the word of the King of the world, which is the greatest good.
Rashi #2: I am prepared to guard the word of kings of nations who rule over us with head-taxes, tithes and plots.
Ibn Ezra: After warning the Chacham to beware of the pitfall of desire, he warns not to rely on his Chachmah to despise the king of his place, [even though] the king is a Kesil compared to the Chacham.
Ri Kara (6): I am obligated to guard the command of a mortal king. All the more so I must guard Hashem's Mitzvos!
R. Avigdor: It is the One about whom it says "Shma Yisrael Hashem
The verse does not call Him 'Melech', but it is the ultimate acceptance of His kingship. In Musaf of Rosh Hashanah, we recite it for the final verse of kingship. (PF)
What is "[v'Al] Divras Shevu'as Elokim"?
Rav Sadya Gaon: The tradition of the Hashem's Bris (covenant with Bnei Yisrael).
Rashi #1: We swore to Him on Sinai to guard His Mitzvos.
Rashi #2: [I will guard the word of kings of nations] on condition that they not force me to transgress the Shevu'ah that we swore to Hashem 1 . Based on the word of the oath of Hashem, I will guard the king's word. So Chananyah, Misha'el and Azaryah told Nebuchadnetzar, you are king over us for work, taxes and head-taxes. For telling us to serve idolatry, you are Nebuchadnetzar, and not a king; you are equal to a dog.
Ibn Ezra: It is what came out of your mouth towards Hashem. A king does not cleanse one who rebels against his word (Yehoshua 1:18) - the true King will not cleanse one who says His name in vain (does not guard his path - Shemos 20:7).
Rashbam: It is what I swore to Hashem that I will do.
Ri Kara: Your Shevu'ah to Hashem obligates you to guard the mouth of a king that you appointed over yourselves.
Ri Kara (6): It is "Le'avrecha bi'Vris Hashem Elokecha uv'Alaso" (Devarim 29:11).
R. Avigdor: It says Divras due to "va'Ydaber Elokim Es Kol ha'Devarim"; Shevu'as refers to "Lo Sisa Es Shem Hashem Elokecha la'Shav" (Shemos 20:1, 7).
Metzudas Tziyon: "V'Al" is like v'Etzel. Divras is an expression of Dibur.
