A command can express no more than an ought or a shall, because it is a universal, but it does not express an 'is'; and this at once makes plain its deficiency. Against such commands Jesus sets virtue, i. e., a loving disposition, which makes the content of the command superfluous and destroys its form as a command, because that form implies an opposition between a commander and something resisting the command.
Der Geist des Christentums und sein Schicksal [The Spirit of Christianity and its Fate] (1799)