Plutarch Lycurgus 7

[1] Although Lycurgus thus tempered his civil polity, nevertheless the oligarchical element in it was still unmixed and dominant, and his successors, seeing it swelling and foaming, as Plato says, ¹ imposed as it were a curb upon it, namely, the power of the ephors. It was about a hundred and thirty years after Lycurgus that the first ephors, Elatus and his colleagues, were appointed, in the reign of Theopompus.

[2] This king, they say, on being reviled by his wife because the royal power, when he handed it over to his sons, would be less than when he received it, said: Nay, but greater, in that it will last longer. And in fact, by renouncing excessive claims and freeing itself from jealous hate, royalty at Sparta escaped its perils, so that the Spartan kings did not experience the fate which the Messenians and Argives inflicted upon their kings, who were unwilling to yield at all or remit their power in favour of the people. And this brings into the clearest light the wisdom and foresight of Lycurgus, when we contrast the factions and misgovernment of the peoples and kings of Messenia and Argos, who were kinsmen and neighbours of the Spartans.

[3] They were on an equality with the Spartans in the beginning, and in the allotment of territory were thought to be even better off than they, and yet their prosperity did not last long, but what with the insolent temper of their kings and the unreasonableness of their peoples, their established institutions were confounded, and they made it clear that it was in very truth a divine blessing which the Spartans had enjoyed in the man who framed and tempered their civil polity for them. These events, however, were of later date.