The Commandments Awaken What Is Already Within
Teshuvah
Rav Menahem Azariah observes that the prohibitions of the Torah appear in the future form: "Thou shalt have no other gods"; "Thou shalt not bow down thyself to other gods"; "Thou shalt not swear falsely." He explains this to mean: "I know thou wilt not be guilty of these things, since human nature does not tolerate such crimes, and if sin occurs in this life it can be only a passing episode." The commandments, on the other hand, are in the imperative: "Kabbed," "zakor." These mean: "I command thee nothing new; the good instincts in thee have always been there; they need only to be awakened and developed." This teaching reflects his optimism and his mild nature, which won him the sympathy of all.
Source: Chikur HaDin, iv. 9