Another answer offers The Code of Hammurabi as an even older contender (18th century CEBCE). The Code has even more metaphysical baggage than Ruism, however, since Hammurabi explicitly calls out glorification of, and prosperity for, rulers who advance the Code. In similar way as the Arthasashstra (3rd-2nd century BCE), it's not clear that Hammurabi's Code is not equally a 'manual for the most effective way to manage a population productively' as it could be a statement that the wellbeing of individual people/citizens are the ends to which government is a means. To the extent that Hammurabi insists that citizens know their rights and be able to avail themselves of the law, the whole thing still seems centered on 'so they can properly revere, serve, and bring prosperity to their king' as a central principle.