DEUT478 … our Sages, z"l, said (Kiddushin 39b), "One who sat and did not commit a sin is rewarded like one who performed a mitzvah, as for example, one who had the opportunity to sin and saved [himself] from doing so." They further said (see Midrash Tehillim 1), "'[A book of remembrance was written before Him" for those who fear Hashem and those who contemplate His Name' (Malachi 3:16) -- this is one who had the opportunity to sin and saved [himself] from doing so." The reward, here too, essentially and fundamentally stems from a positive commandment, for he has prevailed over his yetzer by fearing God, as the pasuk says [this verse], "You shall fear Hashem, your God."