The entire Torah, with all its mitzvos, was given so that a Yid should believe in Hashem.
The Maor v'Shemesh (Yisro במדרש איתא ה"ד) writes in the name of Rebbe Elimelech of Lizhensk zt'l, לאמר האלה הדברים כל את אלקים וידבר אלקיך 'ה אנכי – , "Hashem spoke all these words, to say: "I am Hashem your G-d." This means אלקים וידבר, Hashem spoke, האלה הדברים כל את, all the mitzvos of the Torah, לאמר so that a Yid should say, אלקיך 'ה אנכי, and believe in Hashem.
The Tiferes Shmuel of Alexander zt'l (ד נשא) writes, "Emunah is the primary preparation for receiving the Torah- יחיה באמונתו וצדיק, with emunah, one gives chiyus to all his limbs to become proper vessels for receiving the Torah. About this, Dovid HaMelech said (Tehillim 119:29) בחרתי אמונה דרך [כי] חנני ותורתך, "favor me with Your Torah, for I have chosen the path of emunah."
The Chazon Ish zt'l (Kovetz Igros 3:1) "A lack in emunah is the root... to thinking unimportant and improper thoughts."
The Rebbe of Toldos Aharon zt'l (introduction to Divrei Emunah) explains the pasuk מצותיך כל עזרני רדפוני שקר אמונה , "All your mitzvos are emunah, they pursue me with falsehood, save me." This pasuk refers to the final generation when there will be a lot of falsehoods in the world. As Chazal (Sanhedrin 97.) say, during the ikvisa d'mishicha, the final generation before Moshiach comes, האמת נעדרת , it will be hard to find truth. Currently, we need extra siyata d'shmaya to remain strong. The solution is אמונה מצותיך כל, to be firm with our emunah when רדפוני שקר, falsehood prevails in the world.
The Or LaShamayim of Apta (Parashas Bo ה"ד היום ) teaches, "In the previous generations, the rectification of the soul was achieved through afflictions. These broke the kelipos and removed the covers that separated us from the neshamah. But in the generation before Moshiach, the correction is easy. We don't need afflictions, but rather emunah in Hashem."
