“The purpose of all the mitzvos, and in fact the only reason for Hashem creating us, is that we come to have emunah in Hashem.” Ramban (Shemos 13:16)
“One who commits severe transgressions but nevertheless excels in bitachon is better than one who does not transgress but does not have bitachon.” Vilna Gaon (Even Shleima 3:2)
“The extent to which we lived with emunah is the primary factor that determines the reward we will receive at the time of redemption.” Chofetz Chaim (Machane Yisrael 3:2)