What do we learn from "Rosh Devarecha Emes"?
Kidushin 31a 1 : The end of Your words proves about their beginning. When the nations heard [the first ha'Dibros,] "Anochi..." and "Lo Yihyeh Lecha" (Shemos 20:2-3), they said that He seeks His own honor. Once they heard "Kabed Es Avicha v'Es Imecha", they admitted to Your first words.
Radak #1: From the beginning of the world and forever, Your words and Mishpatim are Emes and Tzedek.
Radak #2: The beginning of what You commanded us is Emes, i.e. Your unity - "Anochi Hashem Elokecha" (Shemos 20:2).
Malbim: Foundations of the Torah are unlike foundations based on human intellect. The latter, even if one reaches Emes, it is not immediately; investigation also researches the side of Sheker. E.g. when one studies Hashem's existence, creation of the world from void, one considers also the other side, whether or not there is a G-d, or if the world was created or is Kadmon (always existed). The foundations that Hashem put in the Torah are only on the side of Emes. "Bereishis Bara Elokim" informs that there is Elokim, and he created existence from void. The final letters of "Bereishis Bara Elokim" hint to this; they are the letters of the word Emes.
Rashi says that they heard [and were critical about] also "Lo Sisa" (Shemos 20:7), and retracted after hearing also "Lo Sirtzach" and "Lo Sin'af" (ibid., 13).
What is the meaning of "[ul'Olam Kol] Mishpat Tzidkecha"?
Radak #1: Your Mishpatim, which are just, You commanded that we guard them forever. They have no time limit, unlike the errant Notzerim say.
Radak #2: Since You commanded us to understand Your unity, it is upon us to always guard all Your just Mishpatim, for they are like a ladder to ascend to knowing Your unity.
Malbim: Mishpat that Hashem established is unlike human codes, which change based on the time and people's mindsets. Your just Mishpat stands forever; it is Emes at all times and in all cases.
